SPM solution mixed acid output control method

Abstract

【Problem】To provide a method for controlling the mixed acid output of an SPM solution that improves the quality and efficiency of wafer cleaning. 【Solution】In the method of the present invention, before the SPM solution enters the pickling tank, sulfuric acid and hydrogen peroxide are sequentially subjected to first-stage mixing and second-stage mixing based on a predetermined volume ratio in the transport pipeline. The mixed solution output after the first-stage mixing is further supplied to the second-stage mixing. Heating is performed in the first-stage mixing, and the oxygen concentration value of the mixed solution flowing out after the first-stage mixing is monitored in real time. When the oxygen concentration value falls below a value indicating that the reaction is sufficient, sulfuric acid and hydrogen peroxide are additionally added at a predetermined volume ratio during the second-stage mixing, so that the oxygen concentration value of the mixed solution flowing out after the second-stage mixing reaches a value indicating that the reaction is sufficient. By adopting a staged mixing method, the present invention realizes sufficient mixing of sulfuric acid and hydrogen peroxide, achieves accurate control of the temperature, and ensures a complete reaction of the mixed solution. As a result, the mixed solution supplied to the pickling tank meets the cleaning requirements, and the quality and efficiency of wafer cleaning are improved.

Description

[Technical Field]

[0001] The present invention relates to a wafer cleaning process, which belongs to the field of wafer manufacturing process technology, and more particularly to a method for controlling the output of mixed acid in an SPM solution. [Background technology]

[0002] In the cleaning process of semiconductor wafers, tank cleaning equipment is widely used as a dedicated cleaning device using chemicals. Up until now, solutions suitable for different cleaning processes have been developed according to the use of various wafer products.

[0003] Common cleaning processes include film stripping, resist stripping, organic cleaning, and removal of metal surface structures and metal residues. These processes often use activated SPM (sulfuric acid-hydrogen peroxide mixture), which is obtained by mixing sulfuric acid (H2SO4), hydrogen peroxide (H2O2), and ultrapure water. This SPM is mixed at a specified concentration ratio. In addition, activated SPM-sulfuric peroxide mixtures, such as DSP+ with ozonated water, are sometimes used for cleaning.

[0004] The active SPM-sulfuric acid peroxide mixed solution is corrosive to semiconductor materials such as silicon (Si), silicon carbide (SiC), gallium nitride (GaN), and gallium arsenide (GaAs), as well as common metals and organic materials with relatively loose molecular structures, and is therefore widely used in the cleaning process of semiconductor wafers, performing functions such as cleaning, etching, and removal.

[0005] In the SPM pickling process in tank-type equipment, pipes are used to supply sulfuric acid (H2SO4), hydrogen peroxide (H2O2), and ultrapure water, which are then injected into the respective supply pipes, then passed through transport pipes, circulation pipes, circulation pumps, filters, a downstream mixer, a temporary storage tank, and downstream output pipes before being sent to the corresponding pickling tank. This prepares the equipment for cleaning.

[0006] However, this transportation process has defects such as uneven mixing, large temperature control errors, and insufficient reaction. These problems cause fatal defects that reduce the performance of the SPM pickling process in tank-type equipment, resulting in a significant decrease in cleaning capacity. Summary of the Invention [Problem to be solved by the invention]

[0007] The technical problem to be solved by the present invention is to provide a method for controlling the output of mixed acid in an SPM solution, which allows the reaction to proceed sufficiently in the transport pipeline before the SPM solution is sent to the pickling tank, thereby overcoming the drawbacks of the prior art. [Means for solving the problem]

[0008] In order to solve the above technical problems, the present invention employs the following technical solutions. In this method, the SPM solution is produced by mixing sulfuric acid and hydrogen peroxide. Before the SPM solution is sent to the pickling tank, the sulfuric acid and hydrogen peroxide are mixed in a pipeline at a predetermined volume ratio, followed by a first-stage and a second-stage mixing. The mixed solution output after the first-stage mixing is then subjected to a second-stage mixing. Heat is applied during the first-stage mixing, and the oxygen concentration of the mixed solution output after the first-stage mixing is monitored in real time. If the oxygen concentration falls below the oxygen concentration value indicating sufficient reaction, additional sulfuric acid and hydrogen peroxide are added at a predetermined volume ratio during the second-stage mixing until the oxygen concentration of the mixed solution output after the second-stage mixing reaches the oxygen concentration value indicating sufficient reaction.

[0009] The control method of the present invention is realized by sequentially subjecting sulfuric acid and hydrogen peroxide to a first stage of mixing and a second stage of mixing. The oxygen concentration value after the first stage of mixing is monitored, and if the oxygen concentration value is below the oxygen concentration value indicating that the reaction is sufficient, sulfuric acid and hydrogen peroxide are added again during the second stage of mixing, thereby allowing the reaction between sulfuric acid and hydrogen peroxide to proceed sufficiently.

[0010] In a further improvement of the present invention, the mixed liquid discharged after the second stage of mixing is subjected to a third stage of mixing in the transport pipeline. If the temperature of the mixed liquid discharged after the first stage of mixing is below the required temperature, heating is continued during the second stage of mixing. Also, if the temperature of the mixed liquid discharged after the second stage of mixing is below the required temperature, further heating is performed during the third stage of mixing. In response to cases where the temperature of the mixed liquid falls below the required temperature in multiple stages, heating is continued at each stage to ensure that the temperature of the mixed liquid reaches the required temperature. This method further improves the accuracy of temperature control and makes it possible to more reliably guarantee the progress of the reaction.

[0011] In a further improvement of the present invention, if the oxygen concentration value of the mixed solution after the second or third mixing stage is below the oxygen concentration value indicating that the reaction is sufficient, sulfuric acid and hydrogen peroxide are additionally added in a predetermined volume ratio during the second mixing stage. By monitoring and adjusting the oxygen concentration of the mixed solution in the latter stages in this way, it is possible to further ensure that the reaction of the mixed solution is proceeding sufficiently.

[0012] In a further improvement of the present invention, if the temperature of the mixed liquid discharged after the second stage of mixing exceeds the required temperature, the mixed liquid is cooled during the third stage of mixing. In this way, if the temperature of the mixed liquid exceeds the required temperature, the temperature is adjusted using circulating cooling water to ensure that the temperature meets the required value, thereby further ensuring the accuracy of temperature control.

[0013] In a specific embodiment of the present invention, the first, second, and third stages of mixing are performed using a mixing pipe having multiple mixing screws inside. In this mixing method, when sulfuric acid and hydrogen peroxide flow into the mixing pipe, they collide with the spiral surface of the mixing screw and rotate. The shear force generated by this rotation causes the sulfuric acid and hydrogen peroxide to penetrate each other. The action of collision and rotation by the multiple mixing screws allows the sulfuric acid and hydrogen peroxide to be thoroughly and uniformly mixed.

[0014] In a specific embodiment of the present invention, the mixed liquid in the mixing pipe is heated by wrapping a heating tube around the outside of the mixing pipe, which makes it possible to heat the mixed liquid while mixing it at the same time.

[0015] The mixed liquid inside the mixing pipe is cooled by circulating cooling water passing through the outside of the mixing pipe, which makes it possible to cool the mixed liquid while mixing it at the same time.

[0016] In a further improvement of the present invention, if the temperature of the mixture discharged after the third stage of mixing is lower than the required temperature, the mixture discharged after the third stage of mixing is supplementarily heated in the transport pipeline, which can further ensure the accuracy of the temperature control.

[0017] Furthermore, the present invention improves the gas pressure in the mixing line by monitoring the gas pressure and depressurizing the mixing line if the gas pressure exceeds a predetermined pressure value. This pressure monitoring and control method ensures the operational safety of the system.

[0018] In a specific embodiment of the present invention, if the mixed liquid after each mixing step meets the required temperature and oxygen concentration, the mixed liquid is directly sent to an SPM storage tank for warm storage and prepared for direct supply to the pickling tank. [Effects of the Invention]

[0019] By adopting the above-mentioned technical measures, the present invention uses a split-stage mixing method to achieve thorough mixing of sulfuric acid and hydrogen peroxide, achieve precise temperature control, and ensure complete reaction of the mixed solution, ensuring that the mixed solution supplied to the pickling tank meets the cleaning requirements, thereby improving the quality and efficiency of wafer cleaning. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a flow diagram of a control method of the present invention. [Figure 2]1 is a structural diagram of a liquid injection system corresponding to the control method of the present invention. [Figure 3] FIG. 2 is a structural diagram of the first mixing device. [Figure 4] FIG. 1 is a structural diagram of a second mixing device. [Figure 5] 1 is a structural diagram of the third mixing device. [Figure 6] 1 is a block diagram showing the electrical connections of the feedback control of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] As shown in FIG. 1, in the SPM solution mixed acid output control method of the present invention, the SPM solution undergoes the processes of first-stage mixing, second-stage mixing, third-stage mixing, and auxiliary heating in sequence in the transport pipeline before entering the pickling tank.

[0022] In the first stage mixing, heating is carried out simultaneously with mixing. Furthermore, the oxygen concentration value of the mixed liquid discharged after the first stage mixing is monitored in real time, and if the oxygen concentration value falls below the oxygen concentration value indicating sufficient reaction, sulfuric acid and hydrogen peroxide are added in a predetermined volume ratio in the second stage mixing until the oxygen concentration value of the mixed liquid discharged after the second stage mixing reaches the value indicating sufficient reaction.

[0023] If the temperature of the mixture flowing out after the first stage mixing is below the required temperature, heating will continue during the second stage mixing. If the temperature of the mixture flowing out after the second stage mixing is below the required temperature, heating will continue during the third stage mixing.

[0024] If the oxygen concentration of the mixed solution is still below the value indicating sufficient reaction after the second or third stage mixing, additional sulfuric acid and hydrogen peroxide are added in the second stage mixing at a predetermined volume ratio.

[0025] Furthermore, if the temperature of the mixed liquid discharged after the second stage mixing exceeds the required temperature, the mixed liquid is cooled in the third stage mixing. This cooling is performed by adjusting the temperature using circulating cooling water so that the temperature of the mixed liquid meets the required value.

[0026] If the temperature of the mixed liquid discharged after the third stage mixing is lower than the required temperature, the mixed liquid discharged after the third stage mixing is supplementally heated on the transport pipeline.

[0027] In this embodiment, the control method of the present invention is implemented using the injection system shown in Fig. 2. This injection system includes a pickling tank 100, a first mixer 200, a second mixer 300, a third mixer 400, a cooling circulation device 500, an SPM storage tank 600, an auxiliary heater 700, and a feedback control board 90.

[0028] The first mixer 200 performs the first stage of mixing. The second mixer 300 performs the second stage of mixing. The third mixer 400 performs the third stage of mixing. The cooling circulation device 500 cools the mixed liquid, and the auxiliary heater 700 performs auxiliary heating of the mixed liquid.

[0029] 3 and 4, the first mixing device 200, the second mixing device 300, and the third mixing device 400 each include a mixing duct 11, a plurality of mixing screws 12 installed in the mixing duct 11, a heater 13 consisting of a heating tube wound around the outside of the mixing duct 11, and a heat insulating layer 14 arranged on the outside of the heater 13. In this embodiment, the heater 13 is composed of a heating tube wound around the mixing duct 11.

[0030] 2 and 3, first mixer 200 has two main input ports 14a at its inlet end and one main output port 14b at its outlet end. The two input ports 14a of first mixer 200 are connected to sulfuric acid source 71 and hydrogen peroxide source 72 via main sulfuric acid line 101 and main hydrogen peroxide line 102, respectively. Main sulfuric acid line 101 and main hydrogen peroxide line 102 are each provided with a flow valve 85.

[0031] 2 and 4, second mixer 300 has one main input port 14a and two sub input ports 14c at its inlet end and one main output port 14b at its outlet end. The two sub input ports 14c of second mixer 300 are connected to sulfuric acid source 71 and hydrogen peroxide source 72 via adjusting sulfuric acid pipe 201 and adjusting hydrogen peroxide pipe 202, respectively. Main input port 14a of second mixer 300 is connected to main output port 14b of first mixer 200 via a main pipe. Adjusting sulfuric acid pipe 201 and adjusting hydrogen peroxide pipe 202 are each provided with a flow valve 85.

[0032] 2 and 5, the third mixer 400 has a cooling circulation channel 24 between the heating pipe 13 and the insulating layer 14. The third mixer 400 has one main input port 14a at its inlet end and one main output port 14b at its outlet end. The cooling circulation channel 24 has a cooling liquid inlet 24a and outlet 24b, which are connected to the liquid outlet and liquid inlet of the cooling circulation device 500 via cooling ducts, respectively.

[0033] The main output port 14 b of the first mixer 200 is connected to the main input port 14 a of the second mixer 300 and the first liquid inlet of the SPM storage tank 600 via a first three-way valve 81 .

[0034] The main output port 14b of the second mixer 300 is connected to the main input port 14a of the third mixer 400 and the second liquid inlet of the SPM storage tank 600 via a second three-way valve 82, respectively.

[0035] The main output port 14 b of the third mixer 400 is connected to the liquid inlet of the auxiliary heater 700 and the third liquid inlet of the SPM storage tank 600 via a third three-way valve 83 .

[0036] The liquid outlet of the SPM storage tank 600 and the liquid outlet of the auxiliary heater 700 are connected to the liquid inlet of the pickling tank 100 via a fourth three-way valve 84 .

[0037] The feedback control board 90 is electrically connected to the cooling circulation device 500 and controls the cooling circulation device 500 to supply circulating cooling liquid to the third mixer 400. This function makes it possible to cool the mixed liquid that enters the third mixer 400 and has an excessively high temperature, thereby lowering the temperature of the mixed liquid to an appropriate range.

[0038] 6, the feedback control board 90 is electrically connected to the heater 13 of the first mixing device 200, the heater 13 of the second mixing device 300, the heater 13 of the third mixing device 400, and the auxiliary heater 700. The feedback control board 90 receives temperature feedback from these heaters and can control the three heaters 13 and the auxiliary heater 700 to perform heating operations.

[0039] Furthermore, a thermometer 91 and an oxygen concentration meter 92 are respectively installed at the main output ports of the first mixer 200, the second mixer 300, the third mixer 400, and the pickling tank 100. A pressure gauge 93 and a safety valve 94, which communicate with the inside of the mixing pipe 11, are also installed in the first mixer 200, the second mixer 300, and the third mixer 400. The thermometer 91, the oxygen concentration meter 92, the pressure gauge 93, and the safety valve 94 are all electrically connected to the feedback control board 90.

[0040] Furthermore, the first, second, third and fourth three-way valves 81 , 82 , 83 , 84 and the four flow valves 85 are all electrically connected to the feedback control board 90 .

[0041] The injection system of the present invention realizes output control of the SPM solution mixed acid, and its specific operation method is as follows.

[0042] Sulfuric acid from the sulfuric acid supply source 71 and hydrogen peroxide from the hydrogen peroxide supply source 72 are supplied at a set ratio to the mixing conduit 11 of the first mixer 200 via the main sulfuric acid conduit 101 and main hydrogen peroxide conduit 102. As the sulfuric acid and hydrogen peroxide flow into the mixing conduit 11, they collide with the helical surface of the mixing screw 12 and begin to rotate. The shear force generated by this rotation causes the sulfuric acid and hydrogen peroxide to penetrate each other. Furthermore, the action of collision and rotation by the multiple mixing screws ultimately results in the sulfuric acid and hydrogen peroxide being thoroughly and uniformly mixed.

[0043] During the mixing process, the heater 13 in the first mixer 200 heats the mixed liquid in the mixing pipe. During heating, the heater 13 transmits the heating temperature to the feedback control board 90, and the feedback control board 90 controls the heating temperature of the heater 13 based on the received temperature data.

[0044] A thermometer 91 and an oxygen concentration meter 92 installed at the main output port of the first mixer 200 monitor the temperature and oxygen concentration of the mixed liquid flowing out from the first mixer 200, respectively, and send the results to the feedback control board 90. If the temperature is below the required temperature, the feedback control board 90 uses the heater of the second mixer 300 to continue heating the incoming mixed liquid while the second mixer 300 further mixes the mixed liquid.

[0045] If the oxygen concentration is below the required concentration, it indicates that the reaction is insufficient. In this case, the feedback control board 90 opens the flow valves of the adjusting sulfuric acid pipe 201 and the adjusting hydrogen peroxide pipe 202, and adds sulfuric acid and hydrogen peroxide to the second mixer 300 at the set ratio to allow the reaction to proceed sufficiently.

[0046] A thermometer installed at the main output port of the second mixer 300 further monitors the temperature of the mixed liquid flowing out of the second mixer 300 and sends the data to the feedback control board 90. If the temperature exceeds the required temperature, the feedback control board 90 controls the circulating cooling device 500 to cause circulating cooling liquid to flow into the cooling channel of the third mixer 400 to cool the mixed liquid. Conversely, if the temperature is below the required temperature, the feedback control board 90 controls the heater in the third mixer 400 to heat the mixed liquid.

[0047] A thermometer installed at the main output port of the third mixer 400 further monitors the temperature of the mixed liquid flowing out of the third mixer 400 and sends the data to the feedback control board 90. If the temperature is still below the required temperature, the auxiliary heater 700 is used to further heat the mixed liquid until the mixed liquid finally meets the required temperature.

[0048] An oxygen concentration meter 92 installed at the main output port of the second mixer 300 and an oxygen concentration meter 92 installed at the main output port of the third mixer 400 monitor the oxygen concentration of the outflowing mixed liquid and send the data to the feedback control board 90. If the oxygen concentration at either point falls below the required concentration, the feedback control board 90 opens the flow valves of the adjusting sulfuric acid pipe 201 and the adjusting hydrogen peroxide pipe 202 to add sulfuric acid and hydrogen peroxide to the second mixer 300 at a predetermined ratio to allow the reaction to proceed sufficiently.

[0049] During the mixing process, pressure gauges monitor the internal pressure of the first mixer 200, the second mixer 300, and the third mixer 400, and transmit the data to the feedback control board 90. If the gas pressure in any mixer exceeds the set value, the feedback control board 90 controls and opens the safety valve of the corresponding mixer to reduce pressure and ensure the safety of the system.

[0050] When the mixed liquid output from each mixing device is sufficiently mixed and the temperature and oxygen concentration meet the required values, the first three-way valve 81, second three-way valve 82, and third three-way valve 83 of the corresponding mixing device can be switched to send the mixed liquid directly to the SPM storage tank 600 and store it at a constant temperature.

[0051] By switching the fourth three-way valve 84, it is possible to select whether the mixed liquid is supplied from the SPM storage tank 600 to the pickling tank 100 or whether the mixed liquid is supplied directly to the pickling tank through an adjustment pipe.

[0052] As can be seen from the above detailed description, the present invention employs a split-stage mixing method to achieve thorough mixing of sulfuric acid and hydrogen peroxide, achieve precise temperature control, ensure complete reaction of the mixed solution, and ensure that the mixed solution supplied to the pickling bath meets cleaning requirements, thereby improving the quality and efficiency of wafer cleaning.

Claims

1. A method for controlling the output of a mixed acid SPM solution, in which the SPM solution is produced by mixing sulfuric acid and hydrogen peroxide, comprising: Before the SPM solution enters the pickling tank, the sulfuric acid and the hydrogen peroxide are mixed in a first stage and a second stage in a pipeline based on a predetermined volume ratio, The mixed liquid output after the first stage mixing is further subjected to a second stage mixing; Heating is performed in the first stage mixing, and the oxygen concentration value of the mixed liquid flowing out after the first stage mixing is monitored in real time; If the oxygen concentration value is below the oxygen concentration value indicating that the reaction is sufficient, sulfuric acid and hydrogen peroxide are additionally added in a predetermined volume ratio during the second stage mixing, so that the oxygen concentration value of the mixed solution discharged after the second stage mixing reaches the oxygen concentration value indicating that the reaction is sufficient; The mixed liquid discharged after the second stage mixing is further subjected to a third stage mixing in a transport pipeline, If the temperature of the mixture flowing out after the first stage mixing is lower than the required temperature, continue heating during the second stage mixing; if the temperature of the mixture flowing out after the second stage mixing is lower than the required temperature, continue heating during the third stage mixing. A method for controlling the output of a mixed acid in an SPM solution.

2. If the oxygen concentration value of the mixed solution after the second or third stage mixing is lower than the oxygen concentration value indicating that the reaction is sufficient, add sulfuric acid and hydrogen peroxide in a predetermined volume ratio during the second stage mixing.

2. The method for controlling the output of a mixed acid in an SPM solution according to claim 1.

3. If the temperature of the mixture discharged after the second stage mixing exceeds the required temperature, the mixture is cooled during the third stage mixing.

2. The method for controlling the output of a mixed acid in an SPM solution according to claim 1.

4. The first stage mixing, the second stage mixing, and the third stage mixing are performed using a mixing pipe having a plurality of mixing screws therein.

4. The method for controlling the output of mixed acid in an SPM solution according to claim 3.

5. The heating method is to wrap a heating tube around the outside of the mixing pipe to heat the mixed liquid inside the mixing pipe.

5. The method for controlling the output of mixed acid in an SPM solution according to claim 4.

6. The cooling method is to pass circulating cooling water through the outside of the mixing pipe to cool the mixed liquid in the mixing pipe.

5. The method for controlling the output of mixed acid in an SPM solution according to claim 4.

7. If the temperature of the mixed liquid flowing out after the third stage mixing is lower than the required temperature, the mixed liquid after the third stage mixing is supplementarily heated on the transport pipeline.

5. The method for controlling the output of mixed acid in an SPM solution according to claim 4.

8. monitor the gas pressure in the mixing pipe, and reduce the pressure in the mixing pipe when the gas pressure exceeds a set pressure value; 5. The method for controlling the output of mixed acid in an SPM solution according to claim 4.

9. If the temperature and oxygen concentration values ​​after each mixing step meet the required values, the mixed liquid is sent directly to the SPM storage tank for warm storage and prepared to be directly supplied to the pickling tank.

5. The method for controlling the output of mixed acid in an SPM solution according to claim 4.

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