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 belonging to the technical field of wafer manufacturing processes, and particularly to a method for controlling the mixed acid output of an SPM solution.

Background Art

[0002] In the cleaning process of semiconductor wafers, the tank-type cleaning device is widely used as a dedicated cleaning device using chemical agents. So far, solutions suitable for different cleaning processes according to the use of various wafer products have been developed.

[0003] Common cleaning processes include film stripping, resist stripping, organic matter cleaning, removal of metal surface structures and metal residues, etc. In these processes, an active SPM (sulfuric acid hydrogen peroxide mixed solution) obtained by mixing sulfuric acid (H2SO4), hydrogen peroxide (H2O2), and ultrapure water is often used. This SPM is mixed at a specified concentration ratio. Furthermore, an activated SPM-peroxymonosulfuric acid mixed solution such as DSP+ with ozone water added may also be used for cleaning.

[0004] The active SPM-peroxymonosulfuric acid mixed solution has a corrosive effect on semiconductor materials such as silicon (Si), silicon carbide (SiC), gallium nitride (GaN), gallium arsenide (GaAs), common metals, and organic substances with a relatively loose molecular structure. Therefore, it performs functions such as cleaning, etching, and removal, and is widely used in the cleaning process of semiconductor wafers.

[0005] In the SPM pickling process in a tank-type device, pipes for supplying sulfuric acid (H2SO4), hydrogen peroxide (H2O2), and ultrapure water are used. After being injected from their respective supply pipes, they pass through a transport pipe, a circulation pipe, a circulation pump, a filter, a mixer in the subsequent stage, a temporary storage tank, and an output pipe in the subsequent stage, and are sent to the corresponding pickling tank. Thereby, the cleaning preparation is carried out.

[0006] However, there are defects in this transportation process, such as non-uniform mixing, large errors in temperature control, and insufficient reaction. These problems cause fatal defects that reduce the capacity of the SPM pickling process in the tank-type device and are factors leading to a significant reduction in cleaning capacity.

Summary of the Invention

Problems 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 mixed acid output of the SPM solution. This control method enables the reaction to proceed sufficiently on the transportation pipeline before the SPM solution is sent to the pickling tank, overcoming the drawbacks existing in the prior art.

Means for Solving the Problems

[0008] To solve the above technical problems, the present invention adopts the following technical means. In this method, the SPM solution is generated by mixing sulfuric acid and hydrogen peroxide. Before the SPM solution is sent to the pickling tank, the sulfuric acid and hydrogen peroxide are sequentially subjected to a first-stage mixing and a second-stage mixing based on a predetermined volume ratio on the transportation pipeline. The mixed solution output after the first-stage mixing is further subjected 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 is lower than the oxygen concentration value indicating sufficient reaction, sulfuric acid and hydrogen peroxide are additionally input 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 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 mixing and a second-stage mixing. By monitoring the oxygen concentration value after the first-stage mixing, when the oxygen concentration value is lower than the oxygen concentration value indicating sufficient reaction, sulfuric acid and hydrogen peroxide are added again during the second-stage mixing, enabling the reaction between sulfuric acid and hydrogen peroxide to proceed sufficiently.

[0010] In a further improvement of the present invention, the mixed liquid flowing out after the second-stage mixing is subjected to a third-stage mixing on a transport pipeline. When the temperature of the mixed liquid flowing out after the first-stage mixing is lower than the required temperature, heating is continued during the second-stage mixing. Also, when the temperature of the mixed liquid flowing out after the second-stage mixing is lower than the required temperature, further heating is performed during the third-stage mixing. In response to the case where the temperature of the mixed liquid is lower than the required temperature in multiple stages, by continuously heating in each stage, it is ensured that the temperature of the mixed liquid reaches the required temperature. By this method, the accuracy of temperature control is further improved, and the progress of the reaction can be more reliably guaranteed.

[0011] In a further improvement of the present invention, when the oxygen concentration value of the mixed liquid after the second-stage mixing or after the third-stage mixing is lower than the oxygen concentration 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. By monitoring and adjusting the oxygen concentration of the mixed liquid in the subsequent stage in this way, it is possible to further ensure that the reaction of the mixed liquid proceeds sufficiently.

[0012] In a further improvement of the present invention, when the temperature of the mixed liquid flowing out after the second-stage mixing exceeds the required temperature, the mixed liquid is cooled during the third-stage mixing. In this way, when the temperature of the mixed liquid exceeds the required temperature, temperature adjustment is performed using circulating cooling water so that the temperature conforms to the required value, thereby further ensuring the accuracy of temperature control.

[0013] In a specific embodiment of the present invention, the first-stage mixing, the second-stage mixing, and the third-stage mixing are performed using a mixing pipeline having a plurality of mixing screws inside. In this mixing method, when sulfuric acid and hydrogen peroxide flow into the mixing pipeline, they collide with the helical surface of the mixing screw and rotate. The shear force generated by this rotation causes sulfuric acid and hydrogen peroxide to penetrate each other. By being subjected to the actions of collision and rotation by a plurality of mixing screws, sulfuric acid and hydrogen peroxide are sufficiently and uniformly mixed.

[0014] In addition, in a specific embodiment of the present invention, the mixed liquid in the mixing pipeline is heated by a method of winding a heating pipe around the outside of the mixing pipeline. By this heating method, it becomes possible to heat the mixed liquid while mixing it.

[0015] Regarding cooling, a method is adopted in which circulating cooling water passes through the outside of the mixing pipeline to cool the mixed liquid in the mixing pipeline. By this cooling method, it becomes possible to cool the mixed liquid while mixing it.

[0016] In a further improvement of the present invention, when the temperature of the mixed liquid flowing out after the third-stage mixing is lower than the required temperature, the mixed liquid flowing out after the third-stage mixing is auxiliary heated on the transport pipeline. By this auxiliary heating method, the accuracy of temperature control can be further ensured.

[0017] Furthermore, in the improvement of the present invention, the gas pressure in the mixing pipeline is monitored, and when the gas pressure exceeds the set pressure value, the mixing pipeline is depressurized. By this pressure monitoring and control method, the operation safety of the system can be ensured.

[0018] In a specific embodiment of the present invention, when the mixed liquid after each mixing stage meets the required values of temperature and oxygen concentration, the mixed liquid is directly sent to the SPM storage tank for heat preservation and storage, and is prepared to be directly supplied to the pickling tank.

Effects of the Invention

[0019] By adopting the above technical means, the present invention realizes sufficient mixing of sulfuric acid and hydrogen peroxide using a staged mixing method, achieves precise temperature control, ensures complete reaction of the mixed liquid, and ensures that the mixed liquid supplied to the pickling tank meets the cleaning requirements. Thereby, the quality and efficiency of wafer cleaning can be improved.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

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Embodiments for Carrying Out the Invention

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

[0022] In the first-stage mixing, heating is carried out while mixing. Furthermore, 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 lower than the oxygen concentration value indicating that the reaction is sufficient, sulfuric acid and hydrogen peroxide are additionally input at a predetermined volume ratio in the second-stage mixing, so that the oxygen concentration value of the mixed liquid flowing out after the second-stage mixing reaches a value indicating a sufficient reaction.

[0023] Also, if the temperature of the mixed liquid flowing out after the first-stage mixing is lower than the required temperature, heating is continued during the second-stage mixing. Furthermore, if the temperature of the mixed liquid flowing out after the second-stage mixing is lower than the required temperature, heating is continued during the third-stage mixing.

[0024] Even after the second-stage mixing or after the third-stage mixing, if the oxygen concentration value of the mixed liquid is lower than the value indicating that the reaction is sufficient, sulfuric acid and hydrogen peroxide are additionally input at a predetermined volume ratio in the second-stage mixing.

[0025] Furthermore, if the temperature of the mixed solution flowing out after the second-stage mixing exceeds the required temperature, the mixed solution is cooled in the third-stage mixing. This cooling utilizes circulating cooling water to adjust the temperature so that the temperature of the mixed solution conforms to the required value.

[0026] If the temperature of the mixed solution flowing out after the third-stage mixing is lower than the required temperature, the mixed solution flowing out after the third-stage mixing is auxiliary heated on the transport pipeline.

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

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

[0029] As shown in FIGS. 3 and 4, each of the first mixing device 200, the second mixing device 300, and the third mixing device 400 includes a mixing pipeline 11, a plurality of mixing screws 12 installed in the mixing pipeline 11, a heater 13 composed of a heating pipe wound around the outside of the mixing pipeline 11, and a heat insulation layer 14 arranged outside the heater 13. The heater 13 of this embodiment is composed of a heating pipe wound around the mixing pipeline 11.

[0030] As shown in FIGS. 2 and 3, the first mixing device 200 is provided with two main input ports 14a at the inlet end and one main output port 14b at the outlet end. The two input ports 14a of the first mixing device 200 are respectively connected to a sulfuric acid supply source 71 and a hydrogen peroxide supply source 72 via a main sulfuric acid pipeline 101 and a main hydrogen peroxide pipeline 102. Flow valves 85 are respectively provided on the main sulfuric acid pipeline 101 and the main hydrogen peroxide pipeline 102.

[0031] As shown in FIGS. 2 and 4, the second mixing device 300 includes one main input port 14a and two sub-input ports 14c at the inlet end, and one main output port 14b at the outlet end. The two sub-input ports 14c of the second mixing device 300 are respectively connected to a sulfuric acid supply source 71 and a hydrogen peroxide supply source 72 via an adjustment sulfuric acid pipeline 201 and an adjustment hydrogen peroxide pipeline 202. The main input port 14a of the second mixing device 300 is connected to the main output port 14b of the first mixing device 200 via a main pipeline. Flow valves 85 are also provided in the adjustment sulfuric acid pipeline 201 and the adjustment hydrogen peroxide pipeline 202 respectively.

[0032] As shown in FIGS. 2 and 5, a cooling circulation channel 24 is provided between the heating pipe 13 and the heat insulation layer 14 in the third mixing device 400. The third mixing device 400 includes one main input port 14a at the inlet end and one main output port 14b at the outlet end. The cooling circulation channel 24 is provided with a coolant inlet 24a and an outlet 24b, which are respectively connected to the liquid outlet and the liquid inlet of the cooling circulation device 500 via cooling pipelines.

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

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

[0035] The main output port 14b of the third mixing device 400 is respectively connected to the liquid inlet of the auxiliary heater 700 and the third liquid inlet of the SPM storage tank 600 via the 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 the 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 that supplies circulating coolant to the third mixing device 400. With this function, it is possible to cool the mixed liquid with an excessively high temperature entering the third mixing device 400 and lower the temperature of the mixed liquid to an appropriate range.

[0038] As shown in FIG. 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 can receive temperature feedback from these heaters and control the three heaters 13 and the auxiliary heater 700 to perform heating operations.

[0039] In addition, thermometers 91 and oxygen concentration meters 92 are installed at the main output ports of the first mixing device 200, the second mixing device 300, the third mixing device 400, and the pickling tank 100, respectively. Pressure gauges 93 and safety valves 94 communicating with the inside of the mixing pipeline 11 are also installed in the first mixing device 200, the second mixing device 300, and the third mixing device 400. All of these thermometers 91, oxygen concentration meters 92, pressure gauges 93, and safety valves 94 are 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 also all electrically connected to the feedback control board 90.

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

[0042] Sulfuric acid is supplied from a sulfuric acid source 71 and hydrogen peroxide is supplied from a hydrogen peroxide source 72 to a mixing pipe 11 of a first mixing device 200 at set ratios via a main sulfuric acid pipe 101 and a main hydrogen peroxide pipe 102, respectively. When the sulfuric acid and hydrogen peroxide flow into the mixing pipe 11, they collide with and rotate along the spiral surface of a mixing screw 12. The shear force generated by this rotation causes the sulfuric acid and hydrogen peroxide to penetrate each other. Furthermore, due to the actions of collision and rotation by a plurality of mixing screws, the sulfuric acid and hydrogen peroxide are finally mixed sufficiently and uniformly.

[0043] During the mixing process, a heater 13 in the first mixing device 200 heats the mixed liquid in the mixing pipe. During heating, the heater 13 transmits the heating temperature to a 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 outlet of the first mixing device 200 monitor the temperature and oxygen concentration of the mixed liquid flowing out of the first mixing device 200, respectively, and transmit them to the feedback control board 90. When the temperature is below the required temperature, during the process of further mixing the mixed liquid in the second mixing device 300, the feedback control board 90 continues to heat the incoming mixed liquid using the heater of the second mixing device 300.

[0045] Also, when 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 an adjusting sulfuric acid pipe 201 and an adjusting hydrogen peroxide pipe 202, and adds sulfuric acid and hydrogen peroxide to the second mixing device 300 at set ratios to allow the reaction to proceed sufficiently.

[0046] The thermometer installed at the main outlet of the second mixing device 300 further monitors the temperature of the mixed liquid flowing out of the second mixing device 300 and transmits the data to the feedback control board 90. When the temperature exceeds the required temperature, the feedback control board 90 controls the circulation cooling device 500 to allow the circulating coolant to flow into the cooling channel of the third mixing device 400 to cool the mixed liquid. Conversely, when the temperature is below the required temperature, the feedback control board 90 controls the heater in the third mixing device 400 to heat the mixed liquid.

[0047] The thermometer installed at the main outlet of the third mixing device 400 further monitors the temperature of the mixed liquid flowing out of the third mixing device 400 and transmits the data to the feedback control board 90. When the temperature is still below the required temperature, the auxiliary heater 700 is used to further heat the mixed liquid so that the mixed liquid finally meets the required temperature.

[0048] The oxygen concentration meter 92 installed at the main outlet of the second mixing device 300 and the oxygen concentration meter 92 installed at the main outlet of the third mixing device 400 monitor the oxygen concentration of the flowing out mixed liquid respectively and transmit the data to the feedback control board 90. When the oxygen concentration is below the required concentration at any position, the feedback control board 90 opens the flow valves of the adjusting sulfuric acid pipeline 201 and the adjusting hydrogen peroxide pipeline 202, adds sulfuric acid and hydrogen peroxide to the second mixing device 300 at a predetermined ratio, and allows the reaction to proceed sufficiently.

[0049] During the mixing process, the pressure gauge monitors the internal pressure of the first mixing device 200, the second mixing device 300, and the third mixing device 400 and transmits the data to the feedback control board 90. When the gas pressure in any mixing device exceeds the set value, the feedback control board 90 controls the safety valve of the corresponding mixing device to open and depressurize to 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, by switching the first three-way valve 81, the second three-way valve 82, and the third three-way valve 83 of the corresponding mixing device, the mixed liquid can be directly sent to the SPM storage tank 600 for heat preservation storage.

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

[0052] As is clear from the above detailed description, by adopting the stepwise mixing method, the present invention realizes sufficient mixing of sulfuric acid and hydrogen peroxide and achieves precise control of the temperature. In addition, it ensures the complete reaction of the mixed liquid and ensures that the mixed liquid supplied to the pickling tank meets the cleaning requirements. As a result, the quality and efficiency of wafer cleaning are improved.

Claims

1. A method for controlling the mixed acid output of an SPM solution 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 sequentially subjected to first-stage mixing and second-stage mixing based on a predetermined volume ratio on a transport pipeline; The mixed solution output after the first-stage mixing is further subjected to 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 is lower than the oxygen concentration value indicating that the reaction is sufficient, sulfuric acid and hydrogen peroxide are additionally input at a predetermined volume ratio during the second-stage mixing, and the oxygen concentration value of the mixed solution flowing out after the second-stage mixing reaches the oxygen concentration value indicating that the reaction is sufficient; A method for controlling the mixed acid output of an SPM solution, characterized by the above.

2. The mixed solution flowing out after the second-stage mixing is further subjected to third-stage mixing on the transport pipeline; When the temperature of the mixed solution flowing out after the first-stage mixing is lower than the required temperature, heating is continued during the second-stage mixing, and when the temperature of the mixed solution flowing out after the second-stage mixing is lower than the required temperature, heating is continued during the third-stage mixing; The method for controlling the mixed acid output of an SPM solution according to claim 1, characterized by the above.

3. When the oxygen concentration value of the mixed solution after the second-stage mixing or after the third-stage mixing is lower than the oxygen concentration value indicating that the reaction is sufficient, sulfuric acid and hydrogen peroxide are additionally input at a predetermined volume ratio during the second-stage mixing; The method for controlling the mixed acid output of an SPM solution according to claim 2, characterized by the above.

4. When the temperature of the mixed solution flowing out after the second-stage mixing exceeds the required temperature, the mixed solution is cooled during the third-stage mixing; The method for controlling the mixed acid output of an SPM solution according to claim 2, characterized by the above.

5. The first-stage mixing, the second-stage mixing, and the third-stage mixing are performed using a mixing pipeline having a plurality of mixing screws inside; The method for controlling the mixed acid output of an SPM solution according to claim 4, characterized by the above.

6. The heating adopts a method of winding a heating pipe outside the mixing pipeline to heat the mixed solution in the mixing pipeline; The method for controlling the mixed acid output of an SPM solution according to claim 5, characterized by the above.

7. The cooling adopts a method of passing circulating cooling water outside the mixing pipeline to cool the mixed solution in the mixing pipeline; The method for controlling the mixed acid output of an SPM solution according to claim 5, characterized by the above.

8. When the temperature of the mixed solution flowing out after the third-stage mixing is lower than the required temperature, the mixed solution after the third-stage mixing is auxiliary heated on the transport pipeline. The method for controlling the mixed acid output of the SPM solution according to claim 5, characterized in that.

9. Monitoring the gas pressure in the mixing pipeline, and when the gas pressure exceeds the set pressure value, performing pressure reduction on the mixing pipeline. The method for controlling the mixed acid output of the SPM solution according to claim 5, characterized in that.

10. When the temperature and oxygen concentration values after the mixing of each stage meet the required values, the mixed solution is directly sent to the SPM storage tank for heat preservation storage and preparation for direct supply to the pickling tank. The method for controlling the mixed acid output of the SPM solution according to claim 5, characterized in that.

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