Subcritical carbon dioxide supply system for chip cleaning

Abstract

The application provides a subcritical carbon dioxide supply system for chip cleaning. The subcritical carbon dioxide supply system for chip cleaning comprises a first conveying pipeline, a second conveying pipeline, a pressure regulating device and a heating device. The pressure regulating device and the heating device are located between the first conveying pipeline and the second conveying pipeline. Liquid carbon dioxide is conveyed in the first conveying pipeline, and gaseous carbon dioxide is conveyed in the second conveying pipeline. The first conveying pipeline comprises a first cooling section and a second cooling section which are sequentially connected. A diaphragm pump is arranged between the first cooling section and the second cooling section. The second conveying pipeline is electrically heated. The temperature of the gaseous carbon dioxide output by the second conveying pipeline is controlled to be 30-40 DEG C, and the pressure is controlled to be 51-59 barg. The subcritical carbon dioxide supply system for chip cleaning provided by the application ensures the stability of subcritical gas through the front-end cooling and rear-end heating mode, and facilitates stable conveying.

Description

Technical Field

[0001] This invention belongs to the field of chip cleaning technology, specifically relating to a subcritical carbon dioxide supply system for chip cleaning. Background Technology

[0002] Cleaning is a crucial step in the entire semiconductor manufacturing process and a significant factor affecting the performance and yield of semiconductor devices. During chip manufacturing, any contamination can impact the performance of semiconductor devices and even cause failure. Therefore, cleaning processes are required before and after almost every step in chip manufacturing to remove surface contaminants and ensure the cleanliness of the wafer surface.

[0003] With the development of very large-scale integrated circuits (VLSI), chip process nodes have entered 28nm, 14nm, and even more advanced nodes. Integration density is constantly increasing, linewidth is constantly decreasing, and the process flow is becoming more complex. Advanced node chip manufacturing is more sensitive to contamination, and cleaning contamination under small-size conditions is more difficult, leading to an increasing number of cleaning process steps, making the cleaning process more complex, important, and challenging. A 90nm chip cleaning process has approximately 90 steps, while a 20nm chip cleaning process reaches 215 steps. As chip manufacturing moves to 14nm, 10nm, and even higher nodes, the number of cleaning process steps will continue to increase.

[0004] As the feature size of integrated circuits gradually decreases, the device structure requires a higher aspect ratio. Conventional wet cleaning methods, due to surface tension, have difficulty penetrating the deep trench structure of the wafer, failing to meet the requirements of finer line processes and high aspect ratio structures, directly affecting the removal effect of contaminants in the trench. Conventional wet etching suffers from poor anisotropy, severe structural collapse, and insignificant deep trench etching effect. In contrast, plasma dry etching has a series of problems such as slow etching rate, photoresist shedding and adhesion, structural damage, and waste gas treatment.

[0005] Supercritical carbon dioxide cleaning can effectively solve these problems. Carbon dioxide reaches a supercritical state at 7.39 MPa and 31℃, exhibiting high density, strong dissolving power, and high mass transfer rate. It also boasts abundant reserves, low cost, non-toxicity, inertness, and ease of recovery and recycling. As a weakly polar solvent, supercritical carbon dioxide has a strong dissolving ability for non-polar organic compounds, effectively removing weakly polar organic contaminants such as silicones, hydrocarbons, and greases from the surfaces of precision devices. Patent publication number CN 209000881 U discloses a cleaning device for Si-based HgCdTe chips before passivation. This device uses carbon dioxide as the cleaning agent; its low surface tension, high diffusivity, and excellent dissolving ability for organic matter improve the cleaning efficiency of contaminants and shorten the cleaning time.

[0006] However, research on the use of supercritical carbon dioxide for chip cleaning is currently limited, with most studies focusing on chip cleaning equipment. A stable carbon dioxide supply is a crucial aspect of chip cleaning, yet research on achieving a stable supply of the necessary carbon dioxide is virtually nonexistent. Unlike other fields, chip cleaning requires a highly stable and continuous carbon dioxide supply. Supply disruptions due to instability can severely impact downstream chip cleaning processes, resulting in significant economic losses. Currently, carbon dioxide is supplied primarily in a supercritical or liquid state. Supercritical carbon dioxide is prone to phase transitions during transport, leading to poor supply stability and difficulty in achieving uninterrupted supply. Liquid carbon dioxide supply, with its lower temperature and pressure, requires a direct conversion from liquid to supercritical state within the chip cleaning plant, which also suffers from instability. Adjustments to the cleaning equipment are needed to achieve a supercritical state, placing high demands on the equipment and resulting in overall poor stability of the cleaning system. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a stable and continuous subcritical carbon dioxide supply system for chip cleaning.

[0008] This invention provides a subcritical carbon dioxide supply system for chip cleaning, comprising a first delivery pipeline, a second delivery pipeline, a pressure regulating device, and a heating device. The pressure regulating device and the heating device are located between the first and second delivery pipelines. Liquid carbon dioxide is delivered in the first delivery pipeline, and gaseous carbon dioxide is delivered in the second delivery pipeline. The first delivery pipeline includes a first cooling section and a second cooling section connected in sequence. A diaphragm pump is installed between the first and second cooling sections. The incoming temperature of the liquid carbon dioxide in the first delivery pipeline is -19°C to -22°C. The average temperature of the first cooling section is controlled between -23°C and -26°C, and the working pressure is 19±4 barg. The average temperature of the second cooling section is controlled between -23°C and -26°C, and the working pressure is 62±4 barg. The second delivery pipeline uses electric heating, and the temperature of the gaseous carbon dioxide output from the second delivery pipeline is controlled between 30°C and 40°C, and the pressure is controlled between 51 barg and 59 barg.

[0009] Preferably, the subcritical carbon dioxide supply system further includes a raw material storage tank and a buffer storage tank, which are connected by a first delivery pipeline. The diaphragm pump is located between the raw material storage tank and the buffer storage tank. The first cooling section is located between the raw material storage tank and the diaphragm pump, and the second cooling section is located between the diaphragm pump and the buffer storage tank. The outlet of the buffer storage tank is connected to the heating device, and the outlet of the heating device is connected to the pressure regulating device.

[0010] Preferably, the inner cylinders of the raw material storage tank and the buffer storage tank are made of S30408 ​​stainless steel, and the thickness of the inner cylinder of the buffer storage tank is 35-45mm.

[0011] Preferably, the second delivery pipeline includes a gas delivery pipe, a heat pipe insulation layer, a heat pipe protective sleeve, and multiple heat tracing sections. From the cross-section of the second delivery pipeline, the heat pipe insulation layer surrounds the gas delivery pipe, the heat pipe protective sleeve surrounds the heat pipe insulation layer, and the multiple heat tracing sections are attached to the outside of the gas delivery pipe. The multiple heat tracing sections are spaced apart along the extension direction of the second delivery pipeline, and each heat tracing section is connected to a separate heat tracing controller.

[0012] Preferably, the heat pipe insulation layer material is foamed polyurethane, the thickness of the heat pipe insulation layer is 90-120mm, and the heat pipe protective sleeve is a stainless steel protective sleeve.

[0013] Preferably, the multiple heat tracing sections include a first heat tracing section, a second heat tracing section, a third heat tracing section, and a fourth heat tracing section arranged sequentially along the second delivery pipeline. The temperatures of the first and third heat tracing sections are controlled to be the same, the temperatures of the second and fourth heat tracing sections are controlled to be the same, and the temperatures of the first and second heat tracing sections are controlled to be different. The first, second, third, and fourth heat tracing sections are spaced 40-60 meters apart. The temperature of the first heat tracing section is controlled at 34°C, and the temperature of the second heat tracing section is controlled at 38°C.

[0014] Preferably, a purifier is also provided on the second delivery pipeline. The purifier is located at the rear end of the pressure regulating device, and the heat tracing cable is located between the purifier and the pressure regulating device. The delivery distance between the heat tracing cable and the purifier is greater than 900 meters.

[0015] Preferably, the first and second cooling sections are transported via cooling pipelines. The cooling pipelines include a liquid delivery pipe and a refrigerant pipeline located outside the liquid delivery pipe. The refrigerant pipeline is connected to a refrigeration unit. Liquid carbon dioxide is transported in the liquid delivery pipe, and ethylene glycol refrigerant flows in the refrigerant pipeline. The ethylene glycol refrigerant is an ethylene glycol solution comprising ethylene glycol and water, wherein the ratio of ethylene glycol to water is 1:(1.21-1.23).

[0016] Preferably, the subcritical carbon dioxide supply system for chip cleaning further includes a cleaning device, the outlet of the second delivery pipeline is connected to the cleaning device to provide gaseous carbon dioxide to the cleaning device, the chip cleaning device is used to adjust the gaseous carbon dioxide to supercritical carbon dioxide, and the chip cleaning device is used to clean the chip with supercritical carbon dioxide.

[0017] The subcritical carbon dioxide supply system for chip cleaning provided by this invention has the following beneficial effects:

[0018] 1. The subcritical carbon dioxide being transported is in a gaseous state, which ensures good transport stability. Furthermore, this condition is close to the supercritical state, making it easy for the chip cleaning equipment to be adjusted to reach the supercritical state, thus providing a stable supply of subcritical carbon dioxide for the chip cleaning equipment.

[0019] 2. A stable and continuous supply of carbon dioxide is achieved by adopting a front-end cooling and rear-end heating method. The front-end cooling is to cooperate with the operation of the diaphragm pump, ensuring that there is sufficient liquid in front of the pump so that it can start in time and ensure stable and continuous delivery. The rear-end heating ensures the stability of the subcritical gas and facilitates stable delivery. Attached Figure Description

[0020] The above and other objects, features, and advantages of the invention will become clearer through a more detailed description of the preferred embodiments illustrated in the accompanying drawings. The same reference numerals denote the same parts throughout the drawings, and the drawings are not intentionally drawn to scale with actual dimensions; the focus is on illustrating the gist of the invention.

[0021] Figure 1 This is a simplified structural diagram of a subcritical carbon dioxide supply system for chip cleaning provided in an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of the second conveying pipeline cross-section provided in an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the overall structure of a subcritical carbon dioxide supply system for chip cleaning provided in an embodiment of the present invention;

[0024] Figure 4 for Figure 3 Enlarged diagram of the "f" part;

[0025] Figure 5 for Figure 3 Enlarged diagram of the "g" part;

[0026] Figure 6 for Figure 5 Enlarged diagram of part "b" in the middle;

[0027] Figure 7 A schematic diagram of the cross-section of the cooling pipeline provided for an embodiment of the invention;

[0028] Figure 8 A schematic diagram of the refrigerant flow direction in the refrigeration unit and diaphragm pump provided in an embodiment of the present invention;

[0029] Figure 9 This is a schematic diagram of the connection structure between the buffer tank and the booster heater provided in an embodiment of the present invention.

[0030] Among them, 1-raw material storage tank, 10-incoming material tank, 2-buffer storage tank, 21-pressurizing heater, 22-soft water supply system, 23-first input pipe, 24-second input pipe, 251-first output pipe, 252-second output pipe, 3-diaphragm pump, 311-pump return pipeline, 4-first conveying pipeline, 40-refrigeration unit, 41-second conveying pipeline, 421-gas conveying pipeline, 422-heat pipe insulation layer, 423-heat pipe protective sleeve, 424-heat tracing cable, 4241-first heat tracing cable, 4242-second heat tracing cable, 4243-third heat tracing cable, 4244-fourth heat tracing cable, 425-heat tracing controller, 51-liquid conveying pipe, 521-refrigerant outlet pipe, 522-refrigerant return pipe, 6-heating device, 7-pressure regulating device. Detailed Implementation

[0031] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to the accompanying drawings.

[0032] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to and integrated with the other component, or there may be an intervening component present. The terms "mounted," "one end," "the other end," and similar expressions used in this document are for illustrative purposes only.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0034] refer to Figure 1-9 This invention provides a subcritical carbon dioxide supply system for chip cleaning, comprising a first delivery pipeline 4, a second delivery pipeline 41, a raw material storage tank 1, a buffer storage tank 2, and a heating device 6. The heating device 6 is located between the first delivery pipeline 4 and the second delivery pipeline 41. Low-temperature liquid carbon dioxide is delivered in the first delivery pipeline 4, and high-temperature gaseous carbon dioxide is delivered in the second delivery pipeline 41. The incoming temperature of the liquid carbon dioxide in the first delivery pipeline 4 is -19°C to -22°C to ensure stable material delivery. The first delivery pipeline 4 includes a first cooling section and a second cooling section connected in sequence. A diaphragm pump 3 is installed between the first cooling section and the second cooling section. The raw material storage tank 1 and the buffer storage tank 2 are connected through the first delivery pipeline 4. The diaphragm pump 3 is located between the raw material storage tank 1 and the buffer storage tank 2. The first cooling section is located between the raw material storage tank 1 and the diaphragm pump 3, and the second cooling section is located between the diaphragm pump 3 and the buffer storage tank 2.

[0035] The incoming liquid carbon dioxide in the feed tank 10 is at a temperature of -19℃ to -22℃ and a working pressure of 19±4 barg. After IQC inspection, it flows into the raw material storage tank 1 (2*60m3).

[0036] Section A extends from raw material storage tank 1 (2*60m3) through the first cooling section to booster pump 3. The working pressure of the first cooling section is 19±4 barg. The entire pipe section adopts strict pipeline insulation measures to ensure that the temperature is between -23℃ and -26℃ and that the liquid is in a supercooled state.

[0037] Section B runs from booster pump 3 to buffer tank 2 (2*20m3), with a working pressure of 62 barg. The entire pipe section adopts strict pipe insulation measures to ensure that the temperature is between -23℃ and -26℃ and that the liquid is in a supercooled state.

[0038] Section C, from buffer tank 2 to heating device 6, operates at a pressure of 62 barg. The entire section of the pipe is protected against freezing and kept cold.

[0039] The D&E section runs from the outlet of the heating device 6 through the pressure regulating device 7 to the delivery point. The second delivery pipeline 41 adopts the form of heat preservation and electric heat tracing to control the gas temperature between 30℃ and 40℃, ensuring a stable supply of gaseous carbon dioxide. The electric heater is configured with 2*750Nm3 / hr.

[0040] In this embodiment, the pressure of the carbon dioxide in the feed tank 10 is low. To facilitate storage and provide high-pressure carbon dioxide to the back end, a booster pump is used on the first delivery pipeline 4 to increase the pressure. Considering that chip cleaning has high requirements for carbon dioxide impurities, a diaphragm pump 3 is used to achieve the booster pump in order to meet the requirements for metal ions in chip cleaning.

[0041] The incoming liquid carbon dioxide is at a temperature of -19°C to -22°C, with an operating pressure of 19±4 barg. Under these conditions, the liquid carbon dioxide is unstable and may partially vaporize, leading to unstable operation of the diaphragm pump 3 and preventing timely startup. This affects stable and continuous delivery, failing to meet the chip cleaning supply requirements. In this embodiment, a cooling system is used in the first and second cooling sections before and after the diaphragm pump 3. Under stable pressure, the temperature of the delivered liquid carbon dioxide is further reduced and controlled to -23°C to -26°C, ensuring that the carbon dioxide is fully liquid before the pump. This allows the diaphragm pump 3 to start at any time when needed, guaranteeing a stable and continuous supply of carbon dioxide.

[0042] The liquid carbon dioxide transported in the first delivery pipeline 4 is pressurized by the diaphragm pump 3, and then further pressurized by the heating device 6 and pressure regulating device before being converted into gaseous carbon dioxide and transported in the second delivery pipeline 41. The second delivery pipeline 41 uses electric heating to control temperature stability. This ensures that the output gaseous carbon dioxide is subcritical carbon dioxide, with the temperature controlled between 30°C and 40°C and the pressure controlled between 51 barg and 59 barg. Under these conditions, the subcritical carbon dioxide is gaseous, has good delivery stability, and these conditions are close to the supercritical state, making it easy for the chip cleaning equipment to adjust to achieve the supercritical state, thus providing a stable supply of subcritical carbon dioxide for the chip cleaning equipment.

[0043] Existing carbon dioxide storage tanks are made of 16MnDR material. During the filling process, some moisture inevitably enters through the filling hose, which accumulates over time. CO2 dissolves in water to produce carbon dioxide, which is weak and corrodes the inner wall of the tank, causing rust and excessive metal ion levels. Therefore, existing carbon dioxide storage tanks are unsuitable for chip cleaning. In this embodiment, the inner cylinders of raw material storage tank 1 and buffer storage tank 2 are made of S30408 ​​stainless steel. Testing shows that the metal ion content of the output carbon dioxide meets the requirements. Furthermore, the wall thickness of buffer storage tank 2 is 35-45mm, which can meet the requirements for storing and buffering high-pressure carbon dioxide liquid, ensuring stable carbon dioxide delivery.

[0044] refer to Figure 2 In a preferred embodiment, the second delivery pipeline 41 is a heat tracing pipeline, including a gas delivery pipe 421, a heat pipe insulation layer 422, a heat pipe protective sleeve 423, and multiple heat tracing sections 424. From the cross-section of the second delivery pipeline 41, the heat pipe insulation layer 422 surrounds the gas delivery pipe 421, the heat pipe protective sleeve 423 surrounds the heat pipe insulation layer 422, and the multiple heat tracing sections 424 are attached to the outside of the gas delivery pipe 421. The multiple heat tracing sections 424 are spaced apart along the extension direction of the second delivery pipeline 41, and each heat tracing section 424 is connected to a separate heat tracing controller 425. The heat tracing sections 424 are equipped with temperature probes for detection. In this embodiment, the heat pipe insulation layer 422 is made of foamed polyurethane, with a thickness of 90-120 mm, and the heat pipe protective sleeve 423 is a stainless steel protective sleeve.

[0045] In this embodiment, electric heating is used through the second delivery pipeline 41, which can effectively maintain the temperature of gaseous carbon dioxide and ensure temperature stability. Simultaneously, the heating tapes 424 are spaced out, and each section of the heating tape 424 has its own controller, enabling segmented control and multi-segment monitoring. This ensures excellent temperature control stability and meets the requirements for a stable and continuous supply for chip cleaning.

[0046] refer to Figure 5-6In a preferred embodiment, the multiple heat tracing cables 424 include a first heat tracing cable 4241, a second heat tracing cable 4242, a third heat tracing cable 4243, and a fourth heat tracing cable 4244, sequentially arranged along the second delivery pipeline 41. The first heat tracing cable 4241, the second heat tracing cable 4242, the third heat tracing cable 4243, and the fourth heat tracing cable 4244 are spaced 40-60 meters apart, ensuring a reasonable spacing between the heat tracing cables 424. This controls the temperature of the first heat tracing cable 4241 and the third heat tracing cable 4243 to be the same, and the temperature of the second heat tracing cable 4242 and the fourth heat tracing cable 4244 to be the same, while controlling the temperature of the first heat tracing cable 4241 and the second heat tracing cable 4242 to be different. The temperature of the first heat tracing cable 4241 is controlled at 34°C, and the temperature of the second heat tracing cable 4242 is controlled at 38°C. This alternating temperature tracing arrangement maintains a stable temperature range for the gaseous carbon dioxide transported by the second delivery pipeline 41, ensuring that the output gaseous carbon dioxide temperature is between 30°C and 40°C.

[0047] refer to Figure 2 In a preferred embodiment, each heat tracing cable 424 includes at least two sets of heat tracing cables 424, which do not operate simultaneously. One set is kept in reserve to ensure the stability of temperature control.

[0048] In a preferred embodiment, a purifier (not shown) is also installed on the second delivery pipeline 41. Because the CO2 throttling and expansion effect causes a certain temperature drop when the pressure is adjusted from 65 kg to about 55 kg, the multi-section heating tape 424 is located between the purifier and the pressure regulating device 7. The liquid carbon dioxide output from the first delivery pipeline 4 is converted into gaseous carbon dioxide through the heating device 6 and the pressure regulating device 7, and then purified by the purifier.

[0049] In a further preferred embodiment, the purifier is located downstream of the pressure regulating device 7, and the multi-section heating cable 424 is located between the purifier and the pressure regulating device 7. The transmission distance between the heating cable 424 and the purifier is greater than 900 meters, preferably 1000 meters in length before the purifier, to meet the needs of on-site pipelines, pipeline accessories, manual valves, and automatic valves. In this embodiment, the pressure regulating device is set before the purifier. After evaluation, this not only ensures good stability of the transmission pressure but also maintains a good purification effect, meeting the requirements for chip cleaning. The size of the electric heating pipeline is selected as a 40A pipe, with a pressure drop exceeding 2.5 kg, which can well meet the requirements.

[0050] refer to Figure 7-8In a preferred embodiment, the first and second cooling sections are transported by cooling pipelines. The cooling pipelines include a liquid delivery pipe 51 and a refrigerant pipeline located outside the liquid delivery pipe 51. The refrigerant pipeline is connected to the refrigeration unit 40. Liquid carbon dioxide is transported in the liquid delivery pipe 51, and ethylene glycol refrigerant flows in the refrigerant pipeline. The ethylene glycol refrigerant is an ethylene glycol solution, which includes ethylene glycol and water, and the ratio of ethylene glycol to water is 1:(1.21-1.23).

[0051] In this embodiment, the incoming temperature of liquid carbon dioxide is between -19°C and -22°C to provide a more stable supply at the upstream end. At this temperature, there is a risk of vaporization. After entering the cooling system of this embodiment, the liquid carbon dioxide needs to be cooled to -24°C to -26°C. Since the incoming material is a heat source at this temperature, the cooling system of this embodiment needs to select a cold source while also considering antifreeze protection. Ethylene glycol solution is chosen because it has a certain viscosity and antifreeze properties, making it very effective for cooling liquid carbon dioxide. The refrigerant piping includes a working group piping and a standby group piping. The working group piping and the standby group piping do not operate simultaneously; one is for backup. Both the working group piping and the standby group piping include a refrigerant outlet pipe 521 and a refrigerant return pipe 522. Both the refrigerant outlet pipe 521 and the refrigerant return pipe 522 are connected to the refrigeration unit 40. Ethylene glycol refrigerant flows from the refrigeration unit 40 to the diaphragm pump 3 through the refrigerant outlet pipe 521, and then flows back to the refrigeration unit 40 through the refrigerant return pipe 522.

[0052] Considering the effects of cooling capacity and viscosity, the ratio of ethylene glycol to water in the ethylene glycol solution is controlled to be 1:(1.21-1.23).

[0053] In this embodiment, the ratio of ethylene glycol to water is controlled at 1:(1.21-1.23). Under this ratio, the ethylene glycol solution has a suitable cooling capacity and a suitable viscosity. It will not have insufficient cooling capacity due to insufficient ethylene glycol content, nor will it have high viscosity due to high ethylene glycol content, which would further affect the fluidity and cooling capacity. Under this ratio of ethylene glycol solution, it can have a very good cold preservation effect on liquid carbon dioxide.

[0054] In a preferred embodiment, the subcritical carbon dioxide supply system for chip cleaning further includes a cleaning device. The outlet of the second delivery pipeline is connected to the cleaning device to provide gaseous carbon dioxide to the cleaning device. The chip cleaning device is used to adjust the gaseous carbon dioxide to supercritical carbon dioxide and to clean the chip with supercritical carbon dioxide.

[0055] refer to Figure 9In a preferred embodiment, the buffer tank 2 is also connected to a self-pressurization system. The liquid carbon dioxide in the buffer tank 2 flows out of the tank from the bottom through the first output pipe 251 and the second output pipe 252. The first output pipe 251 carries the liquid carbon dioxide to the heating device 6, where it is heated, vaporized, and pressure-regulated before being transported with heat. The second output pipe 252 is connected to the pressurization heater 21 of the self-pressurization system, which pressurizes, heats, and vaporizes the liquid carbon dioxide before it flows back into the tank through the first input pipe 23 and the second input pipe 24 from the top of the tank, thus achieving self-pressurization inside the tank. At the same time, because carbon dioxide is very easy to change phase, in order to ensure a better vaporization effect, the pipeline flowing from the pressurization heater 21 to the buffer tank 2 is the heat-traced pipeline mentioned in the above embodiment, ensuring that the tank can stably provide gas self-pressurization. To further ensure a stable liquid supply to the booster heater 21, the booster heater 21 is also connected to a soft water supply system 22, which provides soft water to the booster heater 21 in addition to liquid carbon dioxide, further ensuring that the tank can stably provide gas for self-pressurization.

[0056] refer to Figure 4 In a preferred embodiment, in addition to the pre-pump reflux of the diaphragm pump, a post-pump reflux pipeline 311 is also provided between the rear end of the diaphragm pump and the buffer tank 2. This diaphragm pump is a standby pump with variable frequency drive. The post-pump reflux ensures that the post-pump pressure is monitored at all times to prevent overpressure. The reflux can be controlled to return to the raw material storage tank during both stationary and running conditions. The post-pump reflux pipeline 311 returns the carbon dioxide liquid to the raw material storage tank 1.

[0057] In the description of this specification, the references to terms such as "preferred embodiment," "another embodiment," "other embodiment," or "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0058] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A subcritical carbon dioxide supply system for chip cleaning, characterized in that, The system includes a first delivery pipeline, a second delivery pipeline, a pressure regulating device, and a heating device. The pressure regulating device and the heating device are located between the first and second delivery pipelines. Liquid carbon dioxide is delivered in the first delivery pipeline, and gaseous carbon dioxide is delivered in the second delivery pipeline. The first delivery pipeline includes a first cooling section and a second cooling section connected in sequence. A diaphragm pump is installed between the first and second cooling sections. The incoming temperature of the liquid carbon dioxide in the first delivery pipeline is -19°C to -22°C. The average temperature of the first cooling section is controlled between -23°C and -26°C, and the working pressure is 19±4 barg. The average temperature of the second cooling section is controlled between -23°C and -26°C, and the working pressure is 62±4 barg. The second delivery pipeline uses electric heating. The temperature of the gaseous carbon dioxide output from the second delivery pipeline is controlled between 30°C and 40°C, and the pressure is controlled between 51 barg and 59 barg. The liquid carbon dioxide delivered in the first delivery pipeline is pressurized by the heating device and regulated by the pressure regulating device, then converted into gaseous carbon dioxide and delivered in the second delivery pipeline.

2. The subcritical carbon dioxide supply system for chip cleaning as described in claim 1, characterized in that, The subcritical carbon dioxide supply system also includes a raw material storage tank and a buffer storage tank, which are connected by a first delivery pipeline. The diaphragm pump is located between the raw material storage tank and the buffer storage tank. The first cooling section is located between the raw material storage tank and the diaphragm pump, and the second cooling section is located between the diaphragm pump and the buffer storage tank. The outlet of the buffer storage tank is connected to the heating device, and the outlet of the heating device is connected to the pressure regulating device.

3. The subcritical carbon dioxide supply system for chip cleaning as described in claim 2, characterized in that, The inner cylinders of the raw material storage tank and the buffer storage tank are made of S30408 ​​stainless steel, and the thickness of the inner cylinder of the buffer storage tank is 35-45mm.

4. The subcritical carbon dioxide supply system for chip cleaning as described in claim 1, characterized in that, The second delivery pipeline includes a gas delivery pipe, a heat pipe insulation layer, a heat pipe protective sleeve, and multiple heat tracing sections. From the cross-section of the second delivery pipeline, the heat pipe insulation layer surrounds the gas delivery pipe, the heat pipe protective sleeve surrounds the heat pipe insulation layer, and the multiple heat tracing sections are attached to the outside of the gas delivery pipe. The multiple heat tracing sections are spaced apart along the extension direction of the second delivery pipeline, and each heat tracing section is connected to a separate heat tracing controller.

5. The subcritical carbon dioxide supply system for chip cleaning as described in claim 4, characterized in that, The heat pipe insulation layer material is foamed polyurethane, the thickness of the heat pipe insulation layer is 90-120mm, and the heat pipe protective sleeve is a stainless steel protective sleeve.

6. The subcritical carbon dioxide supply system for chip cleaning as described in claim 4, characterized in that, The multiple heat tracing sections include a first heat tracing section, a second heat tracing section, a third heat tracing section, and a fourth heat tracing section arranged sequentially along the second delivery pipeline. The temperatures of the first and third heat tracing sections are controlled to be the same, the temperatures of the second and fourth heat tracing sections are controlled to be the same, and the temperatures of the first and second heat tracing sections are controlled to be different. The first, second, third, and fourth heat tracing sections are arranged at intervals of 40-60 meters. The temperature of the first heat tracing section is controlled at 34°C, and the temperature of the second heat tracing section is controlled at 38°C.

7. The subcritical carbon dioxide supply system for chip cleaning as described in claim 4, characterized in that, A purifier is also installed on the second delivery pipeline. The purifier is located at the rear end of the pressure regulating device. The heat tracing cable is located between the purifier and the pressure regulating device. The delivery distance between the heat tracing cable and the purifier is greater than 900 meters.

8. The subcritical carbon dioxide supply system for chip cleaning as described in claim 1, characterized in that, The first and second cooling sections are supplied by cooling pipelines. The cooling pipelines include a liquid delivery pipe and a refrigerant pipeline located outside the liquid delivery pipe. The refrigerant pipeline is connected to a refrigeration unit. Liquid carbon dioxide is delivered in the liquid delivery pipe, and ethylene glycol refrigerant flows in the refrigerant pipeline. The ethylene glycol refrigerant is an ethylene glycol solution, which includes ethylene glycol and water, and the ratio of ethylene glycol to water is 1:(1.21-1.23).

9. The subcritical carbon dioxide supply system for chip cleaning as described in claim 1, characterized in that, The subcritical carbon dioxide supply system for chip cleaning also includes a cleaning device. The outlet of the second delivery pipeline is connected to the cleaning device to provide gaseous carbon dioxide to the cleaning device. The chip cleaning device is used to adjust the gaseous carbon dioxide to supercritical carbon dioxide and to clean the chip with supercritical carbon dioxide.

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