Collection and recycle of rare gases in semiconductor processing equipment

Abstract

The invention relates to collection and recycling of rare gases in semiconductor processing equipment. A processing chamber, for example for a semiconductor processing apparatus, is connected to a recovery unit. The recovery unit includes a first storage tank for buffer gas and a second storage tank for rare gas. And the two storage grooves are connected with the column body in the recovery unit. The recovery unit and process chamber may operate as a closed system. The rare gas may be conveyed at a variable flow rate, while the separation in the recovery unit operates at a constant flow condition.

Description

Collection and recycling of rare gases in semiconductor processing equipment

[0001] Information related to divisional application

[0002] This application is a divisional application of the invention patent application filed on March 12, 2020, with application number 202080018399.X and invention title "Collection and Recycling of Rare Gases in Semiconductor Processing Equipment". Technical Field

[0003] This disclosure relates to semiconductor processing equipment. Background Technology

[0004] The demand for valuable rare gases is constantly increasing. Xenon, a trace component of the atmosphere (87 ppb) and a byproduct of complex air separation processes, is an expensive material for semiconductor processing applications and others. For example, xenon is finding increasing use in applications such as anesthesia, ion propulsion engines, high-intensity discharges in lighting, plasma etching in semiconductor manufacturing, plasma media in discharges, or laser-generated plasmas. The number of these increased applications is generally limited by the finite supply of xenon. Collecting and recycling valuable rare gases like xenon with the highest recovery efficiency would be helpful.

[0005] The recovery efficiency of a rare gas recovery unit affects the amount of rare gas collected. Typical performance ranges from 90% to 99.9%. A residual rare gas (e.g., Xe) is typically lost when the buffer gas is vented or otherwise removed. Depending on the gas separation technology and implementation scheme, improving recovery efficiency may not be feasible or may be expensive.

[0006] The loss of residual rare gases can have a significant impact on the long-term cost of ownership in semiconductor processing tools, for example. The negative impact on the cost of ownership can be particularly severe when the rare gas flow rate is at a high rate of several liters per minute and the processing chamber operates almost 24 hours a day (which is common in semiconductor manufacturing).

[0007] Therefore, there is a need for novel systems and methods for collecting and recycling rare gases. Summary of the Invention

[0008] A system is provided in a first embodiment. The system includes: a processing chamber using xenon and / or krypton; and a recovery unit in fluid communication with the processing chamber. The recovery unit includes: a mixing tank in fluid communication with the processing chamber via a gas discharge line; a first column in fluid communication with the mixing tank; a second column in fluid communication with the mixing tank; a first storage tank in fluid communication with the first column and the processing chamber; a second storage tank in fluid communication with the second column and the processing chamber; a first gas supply line connecting the first storage tank to the processing chamber; a second gas supply line connecting the second storage tank to the processing chamber; a first return line connecting the first gas supply line to the gas discharge line; and a second return line connecting the second gas supply line to the discharge line.

[0009] The gas discharge line may include a vacuum pump.

[0010] The system may further include a compression pump in fluid communication with the mixing tank, the first column, and the second column.

[0011] The recovery unit may use at least one of pressure swing adsorption, vacuum pressure swing adsorption, or temperature swing adsorption.

[0012] The recovery unit can use low-temperature distillation.

[0013] The recycling unit can use membrane separation.

[0014] The recycling unit may be a closed-loop system having the processing chamber.

[0015] The system may further include multiple processing chambers in fluid communication with the gas discharge line, the first gas supply line, and the second gas supply line. Each of the processing chambers can operate at a different gas supply flow rate.

[0016] A second embodiment provides a method. The method includes processing a semiconductor wafer in a processing chamber using a processing gas. The processing gas comprises a rare gas and a buffer gas. The processing gas is pumped from the processing chamber to a mixing tank via a gas discharge line. The processing gas is pumped from the mixing tank to a first column and a second column. The processing gas is separated in the first column and the second column. The buffer gas is delivered from the first column to a first storage tank. The rare gas is delivered from the second column to a second storage tank. The buffer gas is delivered from the first storage tank to the processing chamber, and the rare gas is delivered from the second storage tank to the processing chamber.

[0017] The rare gas may include at least one of xenon or krypton. The buffer gas may include at least one of argon, neon, oxygen, nitrogen, or hydrogen.

[0018] The method may further include diverting at least some of the rare gases from the second gas supply line to the gas discharge line instead of the processing chamber.

[0019] The method may further include diverting at least some of the buffer gases from the first gas supply line to the gas discharge line instead of the processing chamber.

[0020] A vacuum pump can be used to pump the processing gas from the processing chamber into the mixing tank. A compression pump can be used to pump the processing gas from the mixing tank into the first column and the second column.

[0021] The separation can be performed using at least one of pressure swing adsorption, vacuum pressure swing adsorption, or temperature swing adsorption.

[0022] The separation can be performed using low-temperature distillation.

[0023] The separation can be performed using thin-film separation.

[0024] The method can be performed in a closed system.

[0025] The rare gas can be delivered from the second storage tank at a variable flow rate, while the separation is operated under constant flow conditions. Attached Figure Description

[0026] For a more complete understanding of the nature and purpose of this disclosure, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, wherein:

[0027] Figure 1 is a diagram of an embodiment of the system according to the present disclosure.

[0028] Figure 2 is a block diagram of the method according to this disclosure.

[0029] Figure 3 is a diagram of another embodiment of the system according to the present disclosure.

[0030] Figure 4 is a diagram of an embodiment of a system having multiple processing chambers according to the present disclosure; and

[0031] Figure 5 is a diagram of another embodiment of a system having multiple processing chambers according to the present disclosure. Detailed Implementation

[0032] While the claimed subject matter will be described with reference to specific embodiments, other embodiments (including those not providing all the advantages and features set forth herein) are also within the scope of this disclosure. Various structural, logical, procedural, and electronic changes may be made without departing from the scope of this disclosure. Therefore, the scope of this disclosure is defined only with reference to the appended claims.

[0033] The embodiments disclosed herein include gas collection and recirculation systems and methods. Rare gases contained in exhaust gas from the processing chamber can be separated, purified, and resupplyed with minimal loss of high-value rare gases. Lower loss of rare gases (e.g., Xe) reduces the system's cost of ownership. Furthermore, the processing chamber can operate at variable gas supply flow rates, while the recovery unit operates under constant optimized flow conditions to improve the combination of recovery efficiency and purity. Multiple processing chambers can operate at different gas supply flow rates while sharing a single recovery unit.

[0034] In semiconductor processing equipment, rare gases (such as xenon or krypton) are typically supplied to the processing chamber with another buffer gas. This combination includes, but is not limited to, Xe / Ar, Xe / Ne, Xe / He, Xe / O2, Xe / N2, Xe / H2, Kr / Ar, Kr / Ne, Kr / He, Kr / O2, Kr / N2, Kr / H2, Xe / Kr, etc. In the case of discharge or laser-generated plasma, xenon atoms can be highly ionized and excited to various high-energy ion states under electron bombardment or laser fields. The transition between dense electron configuration manifolds results in broadband emission covering infrared (IR), visible light, ultraviolet (UV), extreme ultraviolet (EUV), and X-rays. Buffer gases (such as Ar, Ne, O2, N2, or H2) can be used to slow (and eventually stop) the high-energy Xe or Kr ions to prevent etching of the processing chamber. Although Kr is considered a rare gas, it can be used as a buffer gas for Xe. One or more buffer gases may be used in conjunction with one or more rare gases. Exhaust gas from the processing chamber is pumped out by a vacuum pump and sent to a rare gas recovery unit, where Xe and / or Kr are separated from the buffer gases (e.g., Ar, Ne, O2, N2, or H2). The rare gases may be purified using gas separation techniques. Such purification techniques include adsorption separation, cryogenic distillation (e.g., U.S. Patent No. 9,168,467), or membrane separation. Pressure swing adsorption (e.g., U.S. Patent No. 7,300,497), vacuum pressure swing adsorption (e.g., U.S. Patent No. 8,535,414), and temperature swing adsorption can be used for adsorption separation. The entire contents of the patents disclosed herein are incorporated herein by reference.

[0035] Figure 1 is a diagram of an embodiment of system 100. System 100 includes a processing chamber 101 and a recovery unit 200. The processing chamber 101 is connected to a gas source line 10, which provides a rare gas or a plurality of rare gases and a buffer gas or a plurality of buffer gases. The recovery unit 200 is in fluid communication with the processing chamber 101. The processing chamber 101, which circulates the rare gas and buffer gas, can be part of a semiconductor inspection or metrology system, such as the light source or measurement chamber of system 100. The processing chamber 101 can also be part of a critical dimension metrology system, a photomask inspection system, a laser-generated plasma source, an etching chamber, or other semiconductor processing, inspection, metrology, or re-inspection system. For example, the processing chamber 101 can be part of a xenon plasma focused ion beam system or a xenon plasma etching system. Applications outside the semiconductor industry are also possible. For example, the processing chamber 101 can be part of a xenon thruster test chamber used for space propulsion research.

[0036] The recovery unit 200 includes a mixing tank 105 in fluid communication with a processing chamber 101 via gas discharge lines 11 / 12 / 14, the gas discharge lines 11 / 12 / 14 including a total inflow section 14. A first column 107 and a second column 108 are in fluid communication with the mixing tank 105 via conduits 15 / 16. A first storage tank 109 is in fluid communication with the first column 107 via conduit 17, the processing chamber 101, and the gas discharge lines 11 / 12 / 14. A second storage tank 110 is in fluid communication with the second column 108 via conduit 18, the processing chamber 101, and the gas discharge lines 11 / 12 / 14. Other connections between the second column 108 and the first storage tank 109, or between the first column 107 and the second storage tank 110, are possible. A first gas supply line 23 connects the first storage tank 109 to the processing chamber 101. A second gas supply line 24 connects the second storage tank 110 to the processing chamber 101.

[0037] Gas discharge lines 11 / 12 / 14 may include a vacuum pump 102. Conduits 15 / 16 connecting the mixing tank 105 to the first column 107 and the second column 108 may include a compression pump 106.

[0038] Gas emissions 11 from processing chamber 101 can be pumped out by vacuum pump 102 and sent to recovery unit 200. The received gas in recovery unit 200 is held in mixing tank 105 and then pumped to gas separation columns 107, 108, where it is pressurized by compression pump 106. The packing material, temperature, and pressure (or vacuum) inside gas separation columns 107, 108 can vary depending on the chosen gas separation technology. Generally, purified rare gases (e.g., Xe) and purified buffer gases (e.g., N2) are present at opposite ends of columns 107, 108, where a specific temperature / pressure distribution can be used. The purified rare gases (e.g., Xe) can be stored in a second storage tank 110 and can be returned to processing chamber 101 via a second gas supply line 24. The second storage tank 110 may contain less than 100% rare gases and may contain impurities or small amounts of buffer gases. Purified, low-cost buffer gas (e.g., N2) can be stored in a first storage tank 109 and returned to the processing chamber 101 via a first gas supply line 23. The first storage tank 109 may contain less than 100% buffer gas and may contain impurities or trace amounts of rare gases. Pumps can be used to deliver the gas in the first and second gas supply lines 23, 24.

[0039] System 100 may include a first return line 21 that connects the first gas supply line 23 to the gas discharge lines 11 / 12 / 14. The combination of flow from the first return line 21 and the gas discharge lines 11 / 12 / 14 can form a total inflow section 14.

[0040] System 100 may include a second return line 22 that connects the second gas supply line 24 to the gas discharge line 11 / 12 / 14. The combination of flow from the second return line 22 and the gas discharge line 11 / 12 / 14 forms a total inflow section 14.

[0041] First and second return lines 21 and 22 are provided for the output flow from recovery unit 200. The flow rates of the first gas supply line 23 and the second gas supply line 24 to processing chamber 101 can be adjusted or closed (e.g., using one or more valves) without affecting the state of recovery unit 200. Flow diverted from the first gas supply line 23 is diverted to the first return line 21. Flow diverted from the second gas supply line 24 is diverted to the second return line 22. The flow rate diverted to the first return line 21 or the second return line 22 can range from 0% to 100%, and the first and second return lines 21 and 22 can have different amounts of flow diverted thereto. The gas flow rate in the total inflow section 14 of recovery unit 200 and a portion of the pressure within the total inflow section 14 can be kept constant.

[0042] Gas discharge line 12, first return line 21, second return line 22, first gas supply line 23 and second gas supply line 24 may include check valves or other types of valves.

[0043] System 100 can request specific flow rates of rare gas and buffer gas, delivered via a first gas supply line 23 and a second gas supply line 24. First storage tank 109 and second storage tank 110 can provide constant flow rates exceeding the maximum demand at processing chamber 101. Remaining quantities can be recycled, for example, continuously via recovery unit 200.

[0044] Recovery unit 200 may use one or more of the following: pressure swing adsorption, vacuum pressure swing adsorption, temperature swing adsorption, cryogenic distillation, or membrane separation. Other technologies are possible.

[0045] As shown in Figure 1, a first storage tank 109 is added for buffering gases (e.g., N2), and the buffered gas, similar to rare gases (e.g., Xe), is recycled from the second storage tank 110 to the processing chamber 101. In this example, the recovery unit 200 is a closed-loop system with the processing chamber 101. All residual rare gases in the first storage tank 109 and the first gas supply line 23 are retained in the system with minimal loss.

[0046] Figure 2 is a block diagram of method 300, which can be applied to system 100 of Figure 1. At 301, a semiconductor wafer is processed with a process gas in a processing chamber. The process gas includes a rare gas and a buffer gas. The rare gas may include at least one of xenon or krypton. The buffer gas may include at least one of argon, neon, oxygen, nitrogen, or hydrogen. Other rare gases or buffer gases are also possible.

[0047] At point 302, a vacuum pump is used to pump the process gas from the processing chamber to the mixing tank via a gas discharge line. At point 303, a compressor pump is used to pump the process gas from the mixing tank to the first and second columns. At point 304, the process gas is separated in the first and second columns. Separation can be achieved using one or more of pressure swing adsorption, vacuum pressure swing adsorption or temperature swing adsorption, cryogenic distillation, or thin-film separation.

[0048] At point 305, a buffer gas is supplied from the first column to the first storage tank. At point 306, a rare gas is supplied from the second column to the second storage tank. At point 307, the buffer gas and the rare gas are supplied to the processing chamber. Therefore, method 300 can be performed in a closed system.

[0049] In this example, the rare gas can be delivered at a variable flow rate, while the separation is operated under constant flow conditions.

[0050] In this example, at least some of the rare gases are diverted from the second gas supply line to the gas discharge line, and / or at least some of the buffer gases are diverted from the gas supply line to the gas discharge line. Therefore, some or all of the rare gases and / or buffer gases bypass the processing chamber. For example, the processing chamber may be out of service or under repair, and the gases can be recirculated via a recirculation system until the processing chamber is back online.

[0051] For example, the gas supply to the processing chamber can be shut off, and the processing chamber exhaust can be switched to air when its connection port is closed. The processing chamber can be pumped until a vacuum is reached, and the associated recovery unit can be pre-filled to design operating conditions. The recovery unit can operate with both the first and second return lines fully open. Recovery can then be stabilized for an optimal combination of recovery efficiency and purity. The gas exhaust line can be switched, connected, or opened to the total inflow section. The flow rates of the first and second gas supply lines to the processing chamber can be set. The flow rate of the first return line can be the difference between the output from the first storage tank and the flow rate in the first gas supply line. The flow rate of the second return line can be the difference between the output from the second storage tank and the flow rate in the second gas supply line.

[0052] As shown in Figure 3, system 201 may further include a gas scraper 103 in fluid communication with the processing chamber 101 and the mixing tank 105. The gas scraper 103 may be located on gas discharge lines 11 / 12 / 14. The gas scraper (103) removes contaminants from the processing chamber 101. These contaminants may include O2 leaked into the chamber from ambient air, hydrocarbons from the vacuum lubricant, escaping from the chamber material, or other sources. The gas scraper 103 may include, for example, one or more of a filter, adsorber, cryogenic trap, getter, or catalyst converter.

[0053] As shown in Figure 4, multiple processing chambers 101-1 to 101-4 and multiple vacuum pumps 102-1 to 102-4 may be used in system 202. Although four processing chambers are shown, more or fewer processing chambers may be included. The maximum number of processing chambers may be determined by the performance of recovery unit 200. Each of the processing chambers 101-1 to 101-4 is in fluid communication with gas discharge lines 11 / 12 / 14 and can operate at different gas supply flow rates, for example using a mass flow controller or other controller. Each of the processing chambers is connected via gas source lines 10-1 to 10-4, first gas supply lines 23-1 to 23-4, and second gas supply lines 24-1 to 24-4. Although each chamber has gas source lines 10-1 to 10-4, not all chambers may have gas source lines. Some chambers may only be connected to the first gas supply line and the second gas supply line.

[0054] As shown in system 203 in Figure 5, each of the processing chambers 101-1 to 101-4 may have a separate gas scraper 103-1 to 103-4.

[0055] Using the systems and methods disclosed herein, a fully closed-loop system for gas collection and recirculation can be implemented, resulting in virtually no loss of valuable rare gases. The return line allows the processing chambers to operate at variable gas supply flow rates, while the recovery unit can operate under constant inflow conditions optimized for the best combination of recovery efficiency and purity. Gas scrapers can be added to remove contaminants and / or impurities that affect the performance of the recovery unit or processing chamber. Multiple processing chambers can share a single recovery unit. Each of these processing chambers can operate at different gas supply flow rates. Each of these processing chambers can use a different gas scraper to remove contaminants and / or impurities.

[0056] In the example, the system disclosed herein can operate with only 0.01% rare gas loss. These losses can occur during servicing of any gas scraper or during cleaning of the processing chamber.

[0057] In this example, the xenon laser-generated plasma (LPP) soft X-ray source uses N2 as a buffer gas to stop the generation of high-energy xenon ions in the plasma, preventing chamber etching and damage to optics. This soft X-ray source uses a recovery unit to recover xenon from the N2 buffer gas. In this example, the recovery unit is a commercial pressure swing adsorption (PSA) recovery unit. The use of the embodiments disclosed herein mitigates the risk of any slow, long-term drift or unpredictable lower xenon recovery efficiency from the recovery unit. Recovery efficiency is a factor affecting the cost of ownership of the tool. Sharing a single recovery unit among multiple tools can further reduce the cost of ownership. The recovery unit can be scaled up to the desired flow rate.

[0058] Although this disclosure has been described with respect to one or more specific embodiments, it will be understood that other embodiments of this disclosure may be made without departing from the scope of this disclosure. Therefore, this disclosure is to be considered limited only by the appended claims and their reasonable interpretation.

Claims

1. A system comprising: The processing chamber uses a processing gas containing rare gases and buffer gases; and a recovery unit, wherein the recovery unit is a closed-loop system having the processing chamber to recover the rare gas from the buffer gas, comprising: a mixing tank fluidly connected to the processing chamber via a gas discharge line to receive the processed gas; and a first column fluidly connected to the mixing tank to separate the processed gas; A second column is in fluid communication with the mixing tank to separate the processed gas; A first storage tank is in fluid communication with the first column to receive the buffer gas from the first column; A second storage tank is in fluid communication with the second column to receive the rare gas from the second column; a first gas supply line connects the first storage tank to the processing chamber to deliver the buffer gas from the first storage tank to the processing chamber. A second gas supply line connects the second storage tank to the processing chamber to deliver the rare gas from the second storage tank to the processing chamber; a first return line connects the first gas supply line to the gas discharge line to divert at least some of the buffer gas from the first gas supply line to the gas discharge line instead of the processing chamber; and a second return line connects the second gas supply line to the gas discharge line to divert at least some of the rare gas from the second gas supply line to the gas discharge line instead of the processing chamber.

2. The system of claim 1, wherein the gas discharge line further comprises a vacuum pump.

3. The system of claim 1, further comprising a compression pump in fluid communication with the mixing tank, the first column and the second column.

4. The system according to claim 1, wherein the recovery unit uses at least one of pressure swing adsorption, vacuum pressure swing adsorption, temperature swing adsorption, cryogenic distillation or thin film separation.

5. The system of claim 1, further comprising a plurality of processing chambers in fluid communication with the gas discharge line, the first gas supply line and the second gas supply line, wherein each of the processing chambers operates at a different gas supply flow rate.

6. The system of claim 1, wherein the rare gas comprises at least one of xenon or krypton, and wherein the buffer gas comprises at least one of argon, neon, oxygen, nitrogen, or hydrogen.

7. A method for execution in a closed system, comprising: A semiconductor wafer is processed in a processing chamber using a processing gas comprising a rare gas and a buffer gas; the processing gas is pumped from the processing chamber to a mixing tank via a gas discharge line; the processing gas is pumped from the mixing tank to a first column and a second column; the processing gas is separated in the first column and the second column; the buffer gas is delivered from the first column to a first storage tank; the rare gas is delivered from the second column to a second storage tank; the buffer gas is delivered from the first storage tank to the processing chamber and the rare gas is delivered from the second storage tank to the processing chamber; at least some of the buffer gas is diverted from the first gas supply line to the gas discharge line instead of the processing chamber; and at least some of the rare gas is diverted from the second gas supply line to the gas discharge line instead of the processing chamber.

8. The method of claim 7, wherein the rare gas comprises at least one of xenon or krypton, and wherein the buffer gas comprises at least one of argon, neon, oxygen, nitrogen, or hydrogen.

9. The method of claim 7, wherein a vacuum pump is used to pump the processing gas from the processing chamber to the mixing tank, and a compression pump is used to pump the processing gas from the mixing tank to the first column and the second column.

10. The method of claim 7, wherein the separation uses at least one of pressure swing adsorption, vacuum pressure swing adsorption, temperature swing adsorption, cryogenic distillation, or thin film separation.

11. The method of claim 7, wherein the rare gas is delivered from the second storage tank at a variable flow rate, while the separation is operated under constant flow conditions.

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