System and method for producing ammonia solution with reduced dissolved carrier gas and oxygen content

Abstract

To provide a system for supplying a rinsing liquid comprising ultra-pure water and ammonia gas.SOLUTION: A system (100) for supplying a rinsing liquid including ultrapure water and ammonia gas includes an ultrapure water source (102) configured to supply ultrapure water to a contactor (110), a gas mixture source configured to supply ammonia gas and a carrier gas to the contactor (110), a control unit configured to maintain an operating pressure of the contactor (110) below a pressure threshold, the contactor (110) configured to generate the rinsing liquid, and a pump (150) configured to deliver the rinsing liquid including a gas partial pressure below the pressure threshold to an outlet.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This application generally relates to systems and methods used in wet cleaning operations during the manufacture of semiconductor devices. In particular, this application relates to systems and methods for generating and delivering deionized water having a desired concentration of NH3 for use in semiconductor manufacturing processes.

Background Art

[0002] The processing of wafers, lithography masks, flat panels, and solar panels includes wet processing with various chemicals. These chemicals need to be rinsed away before the treated wafers or panels are dried. Deionized water (DI water) and ultrapure water (used synonymously herein) are commonly used in semiconductor device manufacturing processes for rinsing or wet cleaning operations.

[0003] However, when using a substantially non-conductive liquid such as DI water in a semiconductor manufacturing process, there is a possibility of charge accumulation on the surface of the wafer. This is particularly problematic in manufacturing processes that use a rotating wafer tool. This is because the electroosmotic effect generated by the contact between the wafer and the DI water used in the cleaning operation can cause charge accumulation and, as a result, electrostatic discharge events. These discharge events can damage or destroy structures on the wafer or attach contaminants and unwanted particles to the wafer. Therefore, in order to avoid the generation of static charges during the rinsing process, it is desirable to use a rinsing liquid having a higher conductivity than ultrapure water.

[0004] Existing systems often use conductive cleaning solutions to reduce charge buildup on wafers during wet cleaning. For example, deionized carbon dioxide (DI-CO2) water can be produced by dissolving a gas such as carbon dioxide (CO2) in DI water. However, the acidity of DI-CO2 water can undesirably etch acid-sensitive materials such as copper, cobalt, and other metals commonly used in the wiring (BEOL) stage of wafer manufacturing.

[0005] Another approach uses ammonia (NH3) instead of CO2. For example, a dilute solution of NH3 in DI water is commonly used on wafers or panels with exposed metal layers. By dissolving NH3 in DI water, an alkaline solution with a substantially lower etching rate than DI-CO2 can be created for use in wet cleaning operations.

[0006] However, processing machines (e.g., single wafer spin tools) typically rinse each wafer in a separate chamber, and a manufacturing facility may operate multiple processing machines independently, even though each machine is connected to a common source of resources used during manufacturing, such as DI water supply for wafer rinsing. Furthermore, processing in each chamber is rarely synchronized, resulting in randomly fluctuating rinsing fluid demand.

[0007] Supplying a freshly prepared conductive rinse solution with a precise amount of dissolved NH3 can present significant technical challenges, given the randomly fluctuating flow rates required for servicing asynchronous processing tools. For example, NH3 can be supplied as a concentrated solution or gas. Due to NH3's high solubility in DI water, using NH3 in its gas phase results in complete absorption by the DI water. However, because NH3 gas is highly reactive with DI water, there is a high risk of backflow of DI water into the NH3 gas supply line and NH3 valve if the NH3 flow rate is sufficiently low. This can lead to serious control problems, as the flow characteristics of a gas-filled valve differ significantly from those of a water-filled valve. Therefore, maintaining a stable flow of NH3 gas into DI water is difficult under these conditions, especially if the gas flow is interrupted during normal processes in the manufacturing process. Producing a rinse solution with a small but precise amount of dissolved ammonia gas in DI water is even more challenging.

[0008] Patent Document 1 discloses an apparatus for generating and delivering a conductive cleaning solution containing DI water with dissolved NH3 at a desired concentration to prevent charge buildup on the wafer surface when used in semiconductor manufacturing processes such as wet cleaning. To address the above-mentioned problems caused by the absorption of NH3 into DI water, a carrier gas such as nitrogen can be used to accelerate the dissolution process. The resulting rinse solution has a partial pressure greater than atmospheric pressure due to the carrier gas.

[0009] This gas partial pressure can be problematic in certain applications. Pressure drops due to the supply nozzle can cause bubbles to form the moment the rinse solution is applied to the wafer surface. These bubbles can adhere to the wafer surface and potentially damage structures formed on it. Another problem can arise from dissolved oxygen in the rinse solution, which can corrode metal structures formed on the wafer. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] U.S. Patent Application Publication No. 2018 / 0133665 [Overview of the project] [Problems that the invention aims to solve]

[0011] In light of the above, there is a continuing need for systems and methods for producing and delivering a rinse solution containing DI water having a gas partial pressure lower than atmospheric pressure and a desired concentration of dissolved NH3. Furthermore, there is a need for systems and methods for reducing and / or removing dissolved oxygen from the rinse solution. The technology described herein enables precise control of the gas partial pressure by controlling the carrier gas flow. Furthermore, the concept described herein provides an oxygen reduction system that reduces the oxygen content in the rinse solution while mitigating ammonia stripping. [Means for solving the problem]

[0012] In one embodiment, this technology features a system for supplying a rinse solution containing ultrapure water and ammonia gas. The system includes an ultrapure water source in fluid communication with a contactor. The ultrapure water source is configured to supply ultrapure water to the contactor. The system further includes a gas mixture source in fluid communication with the contactor. The gas mixture source is configured to supply ammonia gas and a carrier gas to the contactor. The system further includes a control unit in fluid communication with the contactor. The control unit is configured to regulate the flow rate of ultrapure water so that the operating pressure of the contactor is kept below a pressure threshold. The system further includes a compressor in fluid communication with the contactor. The compressor is configured to remove residual transfer gas from the contactor. The contactor is configured to produce a rinse solution having ultrapure water and ammonia gas at a concentration dissolved therein. The system further includes a pump in fluid communication between the contactor and an outlet. The pump is configured to deliver the rinse solution to the outlet having a gas partial pressure below a pressure threshold.

[0013] This technology may further include any of the following features: In some embodiments, the control unit is configured to adjust the flow rate of ultrapure water in the contactor inlet in order to control the operating pressure of the contactor.

[0014] In some embodiments, the liquid level of the contactor is controlled by adjusting the flow rate of the carrier gas. In some embodiments, the liquid level in the contactor is controlled by adjusting the flow rate of the residual transfer gas.

[0015] In some embodiments, the operating pressure of the contactor is in the range of approximately 0.4 to approximately 0.95 bar (approximately 40 to approximately 95 kPa) (absolute pressure). For example, in some embodiments, the operating pressure of the contactor is approximately 0.6 bar (60 kPa) (absolute pressure).

[0016] In some embodiments, the pressure threshold is approximately atmospheric pressure. In some embodiments, the rinsing fluid is delivered to the wafer. For example, in some embodiments, the system further includes a nozzle that communicates with the fluid to an outlet. The nozzle may be configured to deliver the rinsing fluid to the wafer.

[0017] In some embodiments, the system further includes a membrane contactor that is in fluid communication with the outlet. For example, in some embodiments, the membrane contactor may be configured to strip oxygen from the rinse fluid.

[0018] In some embodiments, the system further includes a pressure sensor that communicates fluidly with the contactor. For example, in some embodiments, the pressure sensor may be configured to monitor the operating pressure of the contactor.

[0019] In some embodiments, the gas mixture source includes an ammonia gas source and a carrier gas source. For example, in some embodiments, the ammonia gas source is configured to supply ammonia gas to the contactor. In some embodiments, the carrier gas source is configured to supply carrier gas to the contactor.

[0020] In some embodiments, ultrapure water, ammonia gas, and carrier gas are mixed before entering the contactor. In some embodiments, the contactor is a packed column or packed tower type contactor.

[0021] In another embodiment, this technology features a method for supplying a rinsing solution containing ultrapure water having a gas partial pressure lower than atmospheric pressure and containing a desired concentration of dissolved ammonia gas. The method comprises supplying ultrapure water and a gas mixture to a contactor. The gas mixture comprises ammonia gas and a carrier gas. The method further comprises monitoring the operating pressure of the contactor using a pressure sensor in fluid communication with the contactor. The method also comprises generating a rinsing solution within the contactor. The rinsing solution contains ultrapure water and a concentration of ammonia gas dissolved therein. Furthermore, the method comprises adjusting the flow rate of the ultrapure water using a control unit in fluid communication with a pressure sensor so that the operating pressure of the contactor is kept lower than atmospheric pressure. The method also comprises removing residual transfer gas from the contactor using a compressor in fluid communication with the contactor. The method further comprises sending the rinsing solution to the outlet using a pump in fluid communication between the contactor and the outlet. The rinsing solution has a gas partial pressure lower than atmospheric pressure.

[0022] In another aspect, this technology features a system for supplying a rinse liquid. The system includes a rinse liquid source in fluid communication with a membrane contactor. The rinse liquid source is configured to supply a rinse liquid having a first oxygen concentration. The system further includes a nitrogen gas source in fluid communication with the membrane contactor. The nitrogen source is configured to supply nitrogen gas to the membrane contactor. The system also includes a nozzle in fluid communication with the membrane contactor. The nozzle is configured to regulate the flow rate of the nitrogen gas. Additionally, the system includes a membrane contactor configured to generate a stripped rinse liquid from the rinse liquid. The stripped rinse liquid has a second oxygen concentration lower than the first oxygen concentration.

[0023] This technology can further include any of the following features. In some embodiments, the system further includes a pump in fluid communication between the membrane contactor and an outlet. The pump can be configured to send the stripped rinse liquid to the outlet. In some embodiments, the pump is a vacuum pump. For example, in some embodiments, the pump is a chemically inert diaphragm pump or a water ring pump.

[0024] The advantages of the systems and methods described herein will be better understood, along with further advantages, by reference to the following description in conjunction with the accompanying drawings. The drawings are not necessarily to scale and are emphasized rather to illustrate the described embodiments by way of example only.

Brief Description of the Drawings

[0025] [Figure 1] FIG. 1 is a block diagram of an exemplary system for supplying a rinse liquid containing DI water having a gas partial pressure lower than atmospheric pressure and having a desired concentration of dissolved NH3 according to an embodiment of the technology described herein. [Figure 2] FIG. 2 is a diagram showing the generation of bubbles caused by the rinse liquid dispensed onto a wafer from a dispensing nozzle according to an embodiment of the technology described herein. [Figure 3] Figure 3 is a block diagram of an exemplary system for understanding and mitigating bubble formation in rinse solution, according to embodiments of the technology described herein. [Figure 4] Figure 4 is a graph showing the results of tests using three different device designs characterized by a system according to embodiments of the technology described herein. [Figure 5] Figure 5 shows an exemplary tube formed in a helical shape according to an embodiment of the technology described herein. [Figure 6] Figure 6 is a graph showing a comparison of oxygen concentrations at the outlet of an apparatus for generating and delivering a conductive cleaning solution containing DI water with a desired concentration of dissolved NH3, with and without the use of an oxygen removal unit, according to embodiments of the technology described herein. [Figure 7] Figure 7 is a graph showing the effect of N2 gas flow on oxygen concentration in the outlet according to embodiments of the technology described herein. [Figure 8] Figure 8 is a block diagram of an exemplary system for supplying a rinse solution containing DI water with a desired concentration of dissolved NH3 and reduced oxygen content, according to an embodiment of the technology described herein. [Figure 9] Figure 9 is a flow diagram of Method 900 for supplying a rinse solution containing DI water in which NH3 is dissolved at a desired concentration, according to embodiments of the technology described herein. [Modes for carrying out the invention]

[0026] In some embodiments, the systems and methods described herein may include one or more mechanisms or methods for generating and delivering a rinse solution containing DI water having a gas partial pressure lower than atmospheric pressure and a desired concentration of dissolved NH3. The systems and methods described herein may include one or more mechanisms or methods for reducing and / or removing dissolved oxygen from the rinse solution. The systems and methods described herein may include one or more mechanisms or methods for precisely controlling the gas partial pressure by controlling the carrier gas flow. The systems and methods described herein may include one or more mechanisms or methods for an oxygen reduction system that reduces the oxygen content in the rinse solution while mitigating ammonia stripping.

[0027] Figure 1 is a block diagram of an exemplary system 100 for supplying a rinse solution containing DI water having a gas partial pressure lower than atmospheric pressure and a desired concentration of dissolved NH3. System 100 includes at least one ultrapure water source 102, at least one carrier gas source 104, and at least one ammonia gas source 106. Optionally, in some embodiments, the carrier gas source 104 and the ammonia gas source 106 include a gas mixture source. While the carrier gas 104 and ammonia gas 106 can be added to the ultrapure water 102 before entering the contactor 110, those skilled in the art will understand that the carrier gas 104 and / or ammonia gas 106 can be added anywhere in the ultrapure water within system 100. In some embodiments, the contactor 110 is a packed column or packed tower type contactor. Optionally, any kind, number, or type of contactor 110 may be used.

[0028] The contactor 110 operates at a pressure lower than atmospheric pressure. The operating pressure within the contactor 110 is monitored by at least one pressure sensor 120. The pressure sensor 120 is connected to a control unit (not shown) that adjusts operating variables such as the flow rate of ultrapure water 102. Thus, the pressure sensor 120 may be configured in the inlet to maintain the operating pressure, but those skilled in the art will understand that the pressure sensor 120 may be configured elsewhere in the contactor 110. The system 100 includes at least one compressor 140 which may be configured to remove residual transfer gas from the contactor 110 in exhaust 142. In one embodiment, the system 100 includes a level sensor 125 which may be configured to monitor the liquid level within the contactor 110.

[0029] The system 100 includes at least one pump 150. In one embodiment, the pump 150 may be configured to deliver rinsing fluid 160 to a wafer or panel processing machine at the required pressure. In some embodiments, the pump 150 may include a centrifugal pump. For example, the pump 150 may be selectively operable and configured not to operate if it is not sufficiently filled with at least one of the carrier gas, ammonia gas, residual gas, ultrapure water, and / or rinsing fluid. For example, at the start of the system 100, the pump 150 may not be filled with liquid. Therefore, the contactor 110 may be temporarily pressurized during the start-up procedure to allow some water to flow from the contactor 110 to the pump 150. The start-up phase is completed when the contactor 110 has the required liquid level and a minimum liquid flow is achieved.

[0030] The pressure inside the contactor 110 can be controlled by adjusting the water flow to the contactor. In some embodiments, the controlled pressure inside the contactor 110 is in the range of about 0.4 to about 0.95 bar (about 40 kPa to about 95 kPa) (absolute pressure), but those skilled in the art will understand that the contactor 110 can operate at any range of pressures. In some embodiments, the controlled pressure inside the contactor 110 is 0.6 bar (60 kPa) (absolute pressure). In some embodiments, the carrier gas 104 is nitrogen (N2) gas. At any discretion, any range of alternative gases can be used.

[0031] The lower limit of the pressure inside the contactor 110 is determined by the operation of the pump 150, which pressurizes the liquid to supply pressure. Low pressure causes cavitation inside the pump 150. This cavitation can lead to particles in the liquid and is therefore desirable to avoid. These particles are undesirable in semiconductor processes because they can contaminate and damage structures formed on the wafer during manufacturing. In some embodiments, the pump 150 is a bearingless pump that operates on the principle of magnetic levitation. This type of pump operates at very low pressures at which cavitation occurs. Such pumps are advantageous to the present invention. In one example, the pump 150 is the pump system of the Levitronix BPS 2000.

[0032] In some embodiments, the pump 150 can introduce heat into the outflowing liquid. This can significantly affect the operation of the system 100 at low liquid flow rates, where the temperature downstream of the pump 150 may become considerably higher. A change in the liquid temperature can change the conductivity of the liquid.

[0033] In some embodiments, the temperature rise due to the pumping action of pump 150 is used as feedback to a controller that adjusts the supply rate of NH3 accordingly to achieve a constant conductivity. In some embodiments, a heat exchanger is used to control the temperature of the outflowing liquid, where the cooling flow is temperature-controlled. In some embodiments, a Peltier element is used to control the temperature of the outflowing liquid.

[0034] Operating the contactor 110 at very low internal pressure can have drawbacks. For example, it requires higher pump energy, resulting in higher costs at low flow rates and increased temperature.

[0035] The upper limit of the pressure within the contactor 110 is determined by the partial pressure exerted by the carrier gas 104, which can cause bubble formation when the liquid is dispensed onto the wafer in the single wafer processing tool. One of the key factors causing bubble formation is the partial pressure of dissolved gases in the liquid. Bubble nucleation in the liquid can occur when the gas partial pressure is higher than the liquid static pressure. Bubble nucleation can occur with particles as bubble nuclei. This mechanism may be inhibited due to the low particle concentration in ultrapure water.

[0036] Another mechanism that can cause bubble formation is, for example, fluctuations in liquid flow in turbulence. This can create localized conditions of very low liquid pressure for a short period of time, which may be low enough to trigger spontaneous bubble nucleation.

[0037] Furthermore, the shape of the nozzle can cause bubble formation. A smooth nozzle does not produce bubbles in the rinse fluid where the partial pressure of the carrier gas is below the ambient pressure. However, the use of a sharp nozzle can cause bubble formation when the partial pressure of the dissolved carrier gas is low.

[0038] The contactor 110 requires a pressure lower than the desired partial pressure exerted by the carrier gas in the liquid in order to remove the carrier gas from the liquid. Furthermore, the techniques described herein can avoid bubble formation in the liquid dispenser by supplying a liquid with a low gas partial pressure. Figure 2, described below, is a diagram 200 showing bubble formation caused by rinse liquid dispensed onto a wafer from a dispensing nozzle. A pressure (absolute pressure) of about 0.95 bar (about 95 kPa) can avoid bubbles in the dispensing nozzle under substantially optimal conditions. In one embodiment, a pressure of 0.6 bar (60 kPa) inside the contactor 110 allows for stable operation even under unfavorable conditions. Bubble formation can be further reduced by selecting a dispenser shape that avoids steep gradients in liquid flow velocity. Configurations for understanding and mitigating bubble formation in the rinse liquid are described below in reference to Figure 3.

[0039] The flow of the carrier gas (e.g., N2) through system 100 can be subject to certain constraints. For example, a high flow rate of carrier gas 104 increases the amount of NH3 stripped into exhaust gas 142, which is undesirable. Furthermore, a high flow rate of carrier gas 104 requires compressor 140 to use a pump with a larger diaphragm, which adds an undesirable cost. In addition, the gas inside contactor 110 is more or less saturated with water vapor due to its operating principle. As the pressure of such a gas increases, the pressure of the water vapor rises above the saturation pressure, resulting in condensation of water.

[0040] Certain types of compressors require oil for lubrication, which can cause oil contamination of the exhaust gas. Such oil contamination is undesirable. Therefore, in some embodiments, an oil-free diaphragm pump is used in the compressor 140 to compress the exhaust gas. Diaphragm pumps are robust devices that can be used with corrosive gases and withstand humid gases.

[0041] The exhaust gas flow contains undesirable water droplets at the outlet of the compressor 140. In some embodiments, the exhaust gas 142 is diluted with a dry gas. The dry gas may be added between the nozzle 130 and the compressor 140, or downstream of the compressor 140. The amount of dry gas added may be selected so that the relative humidity of the compressed exhaust gas is less than 100%.

[0042] In other embodiments, the exhaust gas is heated by a heat exchanger or heated tube to an amount such that the relative humidity at the achieved temperature is less than 100%. The carrier gas 104 acts to transfer NH3 106 to the contactor 110. Generally, the time delay occurs as a function of the length of the corresponding gas pipe. When the liquid flow rate changes dynamically, a large time delay is undesirable because it affects the stability of the concentration of dissolved NH3 in the liquid. When the liquid flow rate changes dynamically, a fast system reaction is required to avoid the resulting overshoot or undershoot of the NH3 concentration in the rinse solution. When the pressure rises, DI water is sent to the gas line. This is undesirable because NH3 gas is too reactive with DI water, and if the NH3 flow rate is sufficiently low, there is a high risk of DI water flowing back into the NH3 gas supply line and NH3 valve. Therefore, some reaction time is required to detect this case and close the corresponding valve.

[0043] In some embodiments, the carrier gas flow rate is set between 1 slm and 20 slm. In some embodiments, the carrier gas flow rate is 2 slm at a pressure (absolute pressure) of 0.6 bar (60 kPa) inside the contactor 110.

[0044] Using the above system and technology, the partial pressure exerted by the carrier gas in the dispensed rinse fluid 160 can be made lower than the ambient pressure. In some embodiments, the system 100 can meet the demand for rinse fluid 160 for a typical single wafer tool or other tools for rinsing the surface of, for example, a flat panel. The flow rate of the rinse fluid 160 may range from 0.5 liters per minute to 100 liters per minute. In certain embodiments, at least a second flow of DI water is mixed with the flow through the contactor 110 to achieve a higher liquid outlet flow of up to 140 liters per minute.

[0045] Referring to Figure 2, diagram 200 shows bubble generation 230 caused by the rinse liquid 210 being dispensed onto the wafer 240 from the dispensing nozzle 220. As described above, a single wafer tool can use multiple chambers. A single dispensing nozzle 220 can be used to supply liquid to the wafers 240 in each chamber. In some embodiments, the dispensed flow in each chamber may be independent of the actual number of chambers using the rinse liquid 210. This can be achieved by a pressure drop in the dispensing nozzle 220 or an upstream valve, which is typically greater than the pressure drop of the liquid flowing through the liquid distribution tube.

[0046] Figure 3 is a block diagram of system 300 for understanding and mitigating bubble generation in the rinse solution. The oxygen-dissolved liquid is created using ozone water supply system 305 and supplied as liquid Out as DIO3. In some embodiments, ozone water supply system 305 is the LIQUOZON device from MKS Instruments Inc., which operates without ozone generation, but an alternative ozone water supply system can be used.

[0047] The liquid flows through the porous membrane device 310 and is then supplied to the device under test 320. The gas inside the membrane device 310 is sealed between valves 330 and 332. The gas pressure becomes equal to the partial pressure of the liquid flowing through the membrane device 310 over time. A pressure gauge 340 is used to directly measure the partial pressure of the liquid.

[0048] The pressure downstream of the device under test 320 is kept constant by a control loop consisting of a pressure gauge 342, a PID controller 350, and a flow control valve 360. The bubble content in the liquid is measured by two devices 370 and 372. In the illustrated embodiment, the two devices 370 and 372 can be any variety of devices, but include optical measuring devices.

[0049] Figure 4 is a graph showing the results using three different designs of the device under test 320, characterized using System 300: (1) a smooth membrane valve from Gemu Group, (2) a valve with sharp edges from Futurestar Corporation, and (3) a curved tube with an outer diameter of approximately 0.25 inches (6.35 mm) and an inner diameter of approximately 0.15 inches (3.95 mm).

[0050] For characterization, valves 330 and 332 were adjusted to produce the same flow rate at a specified pressure drop. The length of the tubes was selected to produce approximately the same flow rate at this pressure drop. Referring to the results in Figure 4, supersaturation is defined as the difference between the measured pressures, i.e., the pressure measured by pressure gauge 342 minus the pressure measured by pressure gauge 340. Positive supersaturation means that the gas partial pressure is higher than the liquid pressure. Negative supersaturation means that the liquid pressure is higher than the gas partial pressure.

[0051] The bubble content of the liquid flowing from the device under test 320 was measured optically using device 370. As shown, curved tubing and the smooth membrane valve of Gemu Group produced the fewest bubbles. In some embodiments, membrane values ​​are used to set the pressure drop. Optionally, helically shaped tubing is used to set the pressure drop. Figure 5 shows an exemplary helically shaped tubing 500. The pressure drop can be achieved by selecting the appropriate number of turns and the appropriate diameter of the helix.

[0052] As manufacturing processes evolve, feature shapes continue to increase in complexity and size, rinsing wafers with exposed metal layers has become a substantially more demanding and precise process. Rinsing silicon wafers is often combined with surface oxidation to reduce their susceptibility to surface contamination. Rinsing the metal on the opposite side of the wafer must avoid surface oxidation, as this can lead to undesirable corrosion and etching of the metal in the rinsing solution.

[0053] The techniques described herein reduce the oxygen content of the rinse solution. The causes of oxygen contamination of the rinse solution were analyzed. Two causes of oxygen contamination that occur during the rinsing process are the rinse solution itself and the effect of the flow of the rinse solution on the wafer.

[0054] The primary oxygen source in rinse solutions is the oxygen contained within the liquid chemicals that make up the rinse solution. These liquid chemicals are often stored in plastic containers to avoid metal contamination. Plastic containers allow oxygen to permeate the liquid during storage. Therefore, the liquid chemicals can become saturated with atmospheric oxygen over time. In the systems described herein, this oxygen source in the rinse solution is avoided because no liquid chemicals are used to produce the rinse solution. For example, the systems described herein use clean gas and ultrapure water. The gas is handled in metal containers or pipes that do not allow atmospheric oxygen to permeate.

[0055] Generally, ultrapure water (UPW) is the liquid with the lowest oxygen concentration available for use in semiconductor manufacturing facilities. UPW is typically prepared immediately before use, and the oxygen is removed before it is distributed to the various processing tools in the semiconductor manufacturing facility.

[0056] Given these factors and conditions, the remaining cause of oxygen contamination is the penetration of oxygen into the pipes and tubes used for handling and distributing the rinse solution. Thus, the cause of oxygen contamination is characterized.

[0057] Oxygen penetration into plastic pipes and tubes occurs according to known processes. In one embodiment, tubes made from perfluoroalkoxy (PFA) may be used. This material is chosen for aggressive and highly reactive liquids used in semiconductor manufacturing processes due to its high inertness. PFA is compatible with most chemicals and can be used at high temperatures. Tubes and fittings formed from this material are readily available. However, PFA has the disadvantage of having a relatively high gas permeability coefficient. Optionally, tubes may be manufactured from a variety of materials that offer high inertness and availability.

[0058] UPW (Upstream Water) distribution tubes in semiconductor manufacturing facilities are typically made of polyvinylidene fluoride (PVDF). PVDF has a much lower oxygen permeability coefficient than PFA (Particle Fat). Therefore, the UPW itself maintains a low oxygen content throughout the distribution pipe, except for the last line used to connect to semiconductor manufacturing tools. This connection is often formed from PFA due to its high flexibility. It has a higher ratio of liquid flow to tube surface than the main distribution tube formed from PVDF.

[0059] These lines can experience flow stagnation, even during tool maintenance or shutdown. The results of this analysis indicate that the overall contribution of small-diameter PFA tubing to oxygen contamination is measurable. Therefore, the technique described herein utilizes nitrogen-purged double containment in the PFA inlet and outlet tubing of the NH3 dissolution device. This configuration is effective in preventing oxygen penetration into the rinse fluid and requires only moderate effort to implement and achieve.

[0060] By combining oxygen removal with the NH3 dissolution system 100, a further reduction in oxygen content can be achieved. Figure 6 is a graph showing a comparison of oxygen concentrations at the outlet of an apparatus (such as the apparatus described in Patent Document 1) for generating and delivering a conductive cleaning solution containing DI water with a desired concentration of dissolved NH3, with and without using an oxygen removal unit.

[0061] In some embodiments, the oxygen removal unit is a commercially available membrane contactor of type 3M® Liqui-Cel® EXF-4×28 series, but any type and number of oxygen removal units can be used. It can operate with a 28 slm N2 gas flow at ambient pressure. The quality of the N2 can be substantially grade 5.6.

[0062] The oxygen removal capacity of such modules is high enough to be effective in some processes. However, the oxygen removal capacity can be increased if the module is operated at lower N2 gas flow rates. Figure 7 is a graph showing the effect of N2 gas flow on oxygen concentration in the outlet. Membrane contactors do not need to be operated at vacuum pressure, which would add an undesirable cost to the vacuum pump.

[0063] The membrane contactor is selected for its low pressure loss to the liquid flow and its chemical compatibility with the NH3 solution. Low pressure loss to the liquid flow is important to avoid energy input to the liquid due to the pumping action of the pump. High energy requirements for pumping cause undesirable temperature changes in the liquid.

[0064] Figure 8 is a block diagram of an exemplary system 800 for supplying a rinse solution 860 containing DI water with NH3 dissolved at a desired concentration with reduced oxygen content. Similar to system 100, system 800 includes an ultrapure water source 802, a carrier gas source 804, an ammonia gas source 806, a contactor 810, a pressure sensor 820, a level sensor 825, and an exhaust 842. System 800 includes a membrane contactor 870 in combination with an NH3 dissolution system such as system 100, as described above in relation to Figure 1. System 800 also includes a nitrogen gas source 880 and a pump 850.

[0065] To avoid moist off-gas from the membrane contactor 870, the membrane contactor 870 can be operated at a pressure exceeding the ambient pressure. The N2 flow rate from the nitrogen gas source 880 can be adjusted by two fixed nozzles 890 and 892. The inner diameters of nozzles 890 and 892 are selected so that the N2 pressure in the contactor 810 is higher than the ambient pressure and lower than the liquid pressure in the contactor 810. The expansion of the N2 gas in nozzle 890 reduces the relative humidity of the N2 below the saturation point, thus avoiding liquid water at the gas outlet of the membrane contactor 870.

[0066] In some cases, it may be preferable to lower the partial gas pressure in the rinse fluid 860 to below the ambient pressure. Therefore, the membrane contactor 870 can operate at an N2 pressure lower than the ambient pressure, and the vacuum pump 850 can be used at the gas outlet of the membrane contactor 870. The vacuum pump 850 may be a chemically inert diaphragm pump or a water ring pump.

[0067] As described above, the solubility of NH3 is high compared to that of other dissolved gases. Therefore, the stripping effect of NH3 in membrane contactor 870 is surprisingly low. The N2 flow rate can be adjusted so that the loss of NH3 is less than 1% while maintaining a sufficiently high oxygen removal rate.

[0068] Figure 9 is a flow diagram of method 900 for supplying a rinse solution containing ultrapure water with a desired concentration of dissolved ammonia gas having a gas partial pressure lower than atmospheric pressure, according to embodiments of the technology described herein. The ultrapure water and gas mixture can be supplied to a contactor (902). In some embodiments, the contactor is a packed column or packed tower type contactor.

[0069] As described above in relation to Figure 1, the gas mixture includes ammonia gas and a carrier gas. For example, using system 100, an ultrapure water source 102 can supply ultrapure water to the contactor 110, a carrier gas source 104 can supply carrier gas to the contactor 110, and an ammonia gas source 106 can supply ammonia gas to the contactor 110. In some embodiments, the ultrapure water, ammonia gas, and carrier gas are mixed before entering the contactor.

[0070] The operating pressure of a contactor can be monitored using a pressure sensor that is in fluid communication with the contactor (904). For example, using system 100, the operating pressure of contactor 110 can be monitored using pressure sensor 120.

[0071] A rinse fluid can be generated within the contactor (906). As described above in relation to Figure 1, the rinse fluid contains ultrapure water and a concentration of ammonia gas dissolved therein. For example, using system 100, a rinse fluid 160 can be generated within the contactor 110.

[0072] The flow rate of ultrapure water can be adjusted using a control unit that is in fluid communication with a pressure sensor (908). As previously mentioned in relation to Figure 1, the flow rate of ultrapure water can be adjusted so that the operating pressure of the contactor is kept below atmospheric pressure. For example, using system 100, the flow rate of ultrapure water supplied by the ultrapure water source 102 can be adjusted using a control unit that is in fluid communication with a pressure sensor 120. In some embodiments, the control unit is configured to adjust the flow rate of ultrapure water at the inlet of contactor 110. In some embodiments, the operating pressure of contactor 110 is controlled by adjusting the flow rate of carrier gas. In other embodiments, the operating pressure of contactor 110 is controlled by adjusting the flow rate of residual transport gas.

[0073] In some embodiments, the operating pressure of the contactor 110 is in the range of approximately 0.4 to approximately 0.95 bar (approximately 40 to approximately 95 kPa) (absolute pressure). For example, in some embodiments, the operating pressure of the contactor is approximately 0.6 bar (approximately 60 kPa) (absolute pressure).

[0074] Residual transfer gas can be removed from the contactor using a compressor that is in fluid communication with the contactor (910). For example, using system 100, residual transfer gas can be removed from contactor 110 using compressor 140.

[0075] Next, the rinse fluid can be sent to the outlet using a pump that creates a fluid communication between the contactor and the outlet (912). As mentioned above, the rinse fluid has a gas partial pressure lower than atmospheric pressure. For example, using system 100, the rinse fluid 160 can be sent to the outlet using pump 150.

[0076] In some embodiments, the rinse solution 160 is delivered to the wafer. For example, in some embodiments, a dispensing nozzle 220, which is in fluid communication with an outlet, is configured to deliver the rinse solution 210 to the wafer 240.

[0077] In some embodiments, using system 800, a membrane contactor 870, which is in fluid communication with an outlet, is configured to strip oxygen from the rinse fluid 860. For example, in some embodiments, system 800 for supplying the stripped rinse fluid 860 may include a rinse fluid source in fluid communication with the membrane contactor 870. The rinse fluid source may be configured to supply rinse fluid having a first oxygen concentration. In some embodiments, system 800 may include a nitrogen gas source 880 in fluid communication with the membrane contactor 870. For example, in some embodiments, the nitrogen gas source 880 may be configured to supply nitrogen gas to the membrane contactor 870. In some embodiments, system 800 may include a nozzle 890 in fluid communication with the membrane contactor 870. For example, the nozzle 890 may be configured to regulate the flow rate of nitrogen gas. In some embodiments, system 800 may include two nozzles 890 and 892, both of which may be configured to regulate the flow rate of nitrogen gas. In some embodiments, the membrane contactor 870 may be configured to produce the stripped rinse solution 860 from the supplied rinse solution. As described above in relation to Figure 8, the stripped rinse solution 860 has a second oxygen concentration lower than the first oxygen concentration.

[0078] As described in detail above, apparatus such as that described in Patent Document 1 can supply a very dilute ammonia solution for use in the manufacturing rinsing process. This solution can be prepared by directly dissolving ammonia gas in water. To avoid the ammonia fountain effect inside the apparatus, the ammonia gas is diluted with nitrogen gas. The ammonia fountain effect occurs when water and ammonia gas come into contact, the water absorbs the ammonia, and a vacuum is created. Additional traces of dissolved nitrogen and oxygen gases cannot be ignored and can affect the manufacturing process. For example, dissolved nitrogen can cause microbubbles on the wafer surface, leading to defects in the structure on the wafer, and traces of oxygen in the liquid can corrode metals. The systems and methods described in detail above address these concerns by precisely controlling the gas partial pressure of the rinsing solution and stripping the oxygen content from the rinsing solution before applying it to the wafer.

[0079] Modifications, alterations, and other embodiments of those described herein will be conceivable to those skilled in the art without departing from the spirit and scope of the invention. Therefore, the invention is not limited to the exemplary description set forth above. The technical concepts included in this disclosure are described below as an addendum. [Note 1] A system for supplying a rinse solution containing ultrapure water and ammonia gas, An ultrapure water source configured to communicate fluidly with a contactor and to supply ultrapure water to the contactor, A gas mixture source configured to be in fluid communication with the contactor and to supply ammonia gas and carrier gas to the contactor, A control unit that is in fluid communication with the contactor, configured to adjust the flow rate of ultrapure water so that the operating pressure of the contactor is kept below a pressure threshold, A compressor configured to communicate fluidly with the contactor and to remove residual transfer gas from the contactor, The contactor is configured to produce a rinse solution, the rinse solution containing ultrapure water and a concentration of ammonia gas dissolved therein, A system comprising a pump that provides fluid communication between the contactor and the outlet, configured to send a rinse liquid containing a gas partial pressure lower than the pressure threshold to the outlet. [Note 2] The system according to Appendix 1, wherein the control unit is configured to adjust the flow rate of ultrapure water in the inlet of the contactor. [Note 3] The system as described in Appendix 1, wherein the liquid level of the contactor is controlled by adjusting the flow rate of the carrier gas. [Note 4] The system as described in Appendix 1, wherein the liquid level of the contactor is controlled by adjusting the flow rate of the residual transfer gas. [Note 5] The operating pressure of the contactor is in the range of approximately 0.4 to approximately 0.95 bar (approximately 40 to approximately 95 kPa) (absolute pressure), as described in Appendix 1. [Note 6] The operating pressure of the contactor is the system described in Appendix 5, including a pressure (absolute pressure) of approximately 0.6 bar (approximately 60 kPa). [Note 7] The system described in Appendix 1, wherein the pressure threshold is atmospheric pressure. [Note 8] The rinsing solution is delivered to the wafer in the system described in Appendix 1. [Note 9] The system according to Appendix 1, further comprising a nozzle that communicates with the outlet, wherein the nozzle is configured to deliver the rinsing liquid to the wafer. [Note 10] The system according to Appendix 1, further comprising a membrane contactor in fluid communication with the outlet, wherein the membrane contactor is configured to remove oxygen from the rinse liquid. [Note 11] The system according to Appendix 1, further comprising a pressure sensor in fluid communication with the contactor, wherein the pressure sensor is configured to monitor the operating pressure of the contactor. [Note 12] The system as described in Appendix 1, wherein the gas mixture source includes an ammonia gas source and a carrier gas source, the ammonia gas source is configured to supply ammonia gas to the contactor, and the carrier gas source is configured to supply carrier gas to the contactor. [Note 13] The system as described in Appendix 1, wherein the ultrapure water, the ammonia gas, and the carrier gas are mixed before entering the contactor. [Note 14] The system described in Appendix 1, wherein the contactor is a packed column or packed tower type contactor. [Note 15] A method for supplying a rinsing solution containing ultrapure water having a gas partial pressure lower than atmospheric pressure and containing a desired concentration of dissolved ammonia gas, The process involves supplying ultrapure water and a gas mixture containing ammonia gas and a carrier gas to the contactor, The operating pressure of the contactor is monitored using a pressure sensor that is in fluid communication with the contactor, A rinse solution containing the ultrapure water and ammonia gas at a dissolved concentration therein is generated in the contactor, The flow rate of the ultrapure water is adjusted using a control unit that communicates with the pressure sensor, so that the operating pressure of the contactor is kept lower than atmospheric pressure. The process involves using a compressor that is in fluid communication with the contactor to remove residual transfer gas from the contactor, A method comprising using a pump that creates fluid communication between the contactor and the outlet to send the rinse liquid containing a gas partial pressure lower than atmospheric pressure to the outlet. [Note 16] The contactor is a packed column or packed tower type contactor, as described in Appendix 15. [Note 17] A membrane contactor configured to communicate fluidly with the outlet and to receive a rinse solution containing a first oxygen concentration through the outlet, A nitrogen gas source that is in fluid communication with the membrane contactor, and is configured to supply nitrogen gas to the membrane contactor, The membrane contactor further comprises a nozzle that is in fluid communication with the membrane contactor and is configured to adjust the flow rate of the nitrogen gas, The system according to Appendix 1, wherein the membrane contactor is configured to remove oxygen from the received rinse solution so as to produce a rinse solution containing a second oxygen concentration lower than the first oxygen concentration from the received rinse solution. [Note 18] If we refer to the aforementioned outlet as the first outlet, The system according to Appendix 17, further comprising a pump that provides fluid communication between the membrane contactor and a second outlet, the pump configured to deliver the rinse solution containing the second oxygen concentration generated in the membrane contactor to the second outlet. [Note 19] The system as described in Appendix 18, wherein the pump that provides fluid communication between the membrane contactor and the second outlet is a vacuum pump. [Note 20] The system as described in Appendix 19, wherein the vacuum pump is a chemically inert diaphragm pump or a water ring pump.

Claims

1. A system for supplying a rinse solution containing ultrapure water and ammonia gas, An ultrapure water source configured to communicate fluidly with a contactor and to supply ultrapure water to the contactor, A gas mixture source configured to be in fluid communication with the contactor and to supply ammonia gas and carrier gas to the contactor, A control unit that is in fluid communication with the contactor, the control unit configured to keep the operating pressure of the contactor below a pressure threshold, The contactor is configured to produce a rinse solution, the rinse solution containing ultrapure water and a concentration of ammonia gas dissolved therein, The system includes a pump that provides fluid communication between the contactor and the outlet, and is configured to send a rinse liquid containing a gas partial pressure lower than the pressure threshold to the outlet. The control unit is configured to adjust the flow rate of ultrapure water in the inlet of the contactor in order to keep the operating pressure of the contactor below the pressure threshold.

2. The system according to claim 1, wherein the liquid level of the contactor is controlled by adjusting the flow rate of the carrier gas.

3. The system according to claim 1, wherein the liquid level of the contactor is controlled by adjusting the flow rate of the residual transfer gas.

4. The system according to claim 1, wherein the operating pressure of the contactor includes a pressure (absolute pressure) in the range of about 0.4 to about 0.95 bar (about 40 to about 95 kPa).

5. The system according to claim 4, wherein the operating pressure of the contactor includes a pressure (absolute pressure) of about 0.6 bar (about 60 kPa).

6. The system according to claim 1, wherein the pressure threshold is atmospheric pressure.

7. The system according to claim 1, wherein the rinsing solution is sent to a wafer.

8. The system according to claim 1, further comprising a nozzle that communicates with the outlet, wherein the nozzle is configured to deliver the rinsing liquid to the wafer.

9. The system according to claim 1, further comprising a membrane contactor in fluid communication with the outlet, wherein the membrane contactor is configured to remove oxygen from the rinse liquid.

10. The system according to claim 1, further comprising a pressure sensor in fluid communication with the contactor, wherein the pressure sensor is configured to monitor the operating pressure of the contactor.

11. The system according to claim 1, wherein the gas mixture source includes an ammonia gas source and a carrier gas source, the ammonia gas source is configured to supply ammonia gas to the contactor, and the carrier gas source is configured to supply carrier gas to the contactor.

12. The system according to claim 1, wherein the ultrapure water, the ammonia gas, and the carrier gas are mixed before entering the contactor.

13. The system according to claim 1, wherein the contactor is a packed column or packed tower type contactor.

14. A membrane contactor configured to communicate fluidly with the outlet and to receive a rinse solution containing a first oxygen concentration from the outlet, A nitrogen gas source that is in fluid communication with the membrane contactor, and is configured to supply nitrogen gas to the membrane contactor, The membrane contactor further comprises a nozzle that is in fluid communication with the membrane contactor and is configured to adjust the flow rate of the nitrogen gas, The system according to claim 1, wherein the membrane contactor is configured to remove oxygen from the received rinse solution so as to produce a rinse solution containing a second oxygen concentration lower than the first oxygen concentration from the received rinse solution.

15. A method for supplying a rinsing solution containing ultrapure water having a gas partial pressure lower than atmospheric pressure and containing a desired concentration of dissolved ammonia gas, The process involves supplying ultrapure water and a gas mixture containing ammonia gas and a carrier gas to the contactor, The operating pressure of the contactor is monitored using a pressure sensor that is in fluid communication with the contactor, A rinse solution containing the ultrapure water and ammonia gas at a dissolved concentration therein is generated in the contactor, In order to keep the operating pressure of the contactor lower than atmospheric pressure, the flow rate of ultrapure water in the inlet of the contactor is adjusted using a control unit that is in fluid communication with the pressure sensor, A method comprising using a pump that creates fluid communication between the contactor and the outlet to send the rinse liquid containing a gas partial pressure lower than atmospheric pressure to the outlet.

16. The method according to claim 15, wherein the contactor is a packed column or packed tower type contactor.

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