Cooling system

Abstract

To provide a cooling system capable of efficiently performing cooling of an electrostatic chuck in a power saving and space saving manner in processing a semiconductor wafer.SOLUTION: One end of a gas pipeline 15A is attached to a base 11A1, and a chiller 13A is attached to the other end of the gas pipeline 15A. Refrigerant gas is supplied from the chiller 13A and passes through a gass passage inside the base 11A1 to cool the base 11A1. The base 11A1 being cooled cools an electrostatic chuck 3 to cool a wafer. On the other hand, one end of a gas branch pipeline 17A is attached to a base 11A2, and the other end of the gas branch pipeline 17A is connected to a chiller 23 which corresponds to a double use chiller via a gas confluence pipeline 21. In the middle of the gas branch pipeline 17A, a valve 19A is arranged. By lowering a temperature of the electrostatic chuck 3, a temperature of the wafer can be lowered while power consumption is being suppressed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cooling system, and more particularly to a cooling system that can efficiently cool an electrostatic chuck in a power-saving, space-saving manner when processing a semiconductor wafer. [Background technology]

[0002] In recent years, the development of an information-driven society has led to demands for an increase in the number of memory layers and for higher processing accuracy. Against this backdrop, plasma etching is widely used when processing semiconductor wafers such as silicon. With plasma etching, even when the wafer surface is deeply carved using plasma processing, the etching rate can be increased by cooling the wafer, which becomes extremely hot. In particular, cryoetching, a technique for etching insulating films at extremely low temperatures, has been attracting attention in recent years. Cryoetching is said to be a groundbreaking technology that can dramatically increase the etching rate and significantly reduce global warming potential. To achieve this cryoetch, plasma processing is performed by placing the wafer in close contact with the holding surface of a chuck table equipped with a cooling structure.

[0003] An example of the cooling structure of Cryo Etch will be explained based on Figure 6. 6, an electrostatic chuck 3 is disposed in a chamber 1, and a wafer (not shown) is placed on the electrostatic chuck 3. The wafer is attracted to the electrostatic chuck 3 by electrical force. The chamber 1 is evacuated by a vacuum pump 5 and a process gas 7 is introduced based on a semiconductor processing schedule. Radio frequency (RF) power 9 is applied to generate plasma in the chamber 1.

[0004] Since the etching rate decreases when the wafer temperature increases during plasma processing, a base 11 having a gas passage formed therein for passing a refrigerant gas is disposed on the underside of the electrostatic chuck 3, and the refrigerant gas is supplied to the base 11 from a chiller 13 (see, for example, Patent Document 1). The chiller 13 itself is cooled, for example, by water cooling. Furthermore, in order to increase the etching rate, there is a tendency for the power consumption of radio frequency (RF) power 9 to also increase. As a result, the amount of heat generated by the increased power also increases, making it necessary to further dissipate and control the heat using a chiller 13. Due to these circumstances, the cooling capacity required of chillers is gradually increasing, and there is a trend toward larger chillers. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2022-36899 Summary of the Invention [Problem to be solved by the invention]

[0006] However, while larger chillers are configured for high efficiency when operating near their rated output, the lower the refrigerant gas output, the more rapidly their operating efficiency drops when operated below the rated output. This can result in power losses and a corresponding decrease in utility, such as the need for more cooling water to cool the chiller. Furthermore, larger chillers require a larger capacity of cooling water, which can increase the space required for their installation.

[0007] The present invention has been made in view of the above-mentioned conventional problems, and has an object to provide a cooling system that can efficiently cool an electrostatic chuck in a power-saving, space-saving manner when processing a semiconductor wafer. [Means for solving the problem]

[0008] For this reason, the present invention (claim 1) is an invention of a cooling system, which comprises electrostatic chucks respectively arranged in a plurality of chambers, dedicated chillers respectively arranged corresponding to the plurality of chambers for cooling the electrostatic chucks, a dual-purpose chiller for cooling the electrostatic chucks of the plurality of chambers, and a control device for controlling the operation of the plurality of chambers, and is characterized in that by operating the dedicated chiller and the dual-purpose chiller together based on control commands from the control device, it is possible to cover the maximum output required for cooling the electrostatic chucks.

[0009] If one large chiller is used to cover the maximum output required to cool an electrostatic chuck, there is a risk that cooling efficiency will decrease in areas with low output. However, by operating a dedicated chiller and a dual-purpose chiller together, efficient operation is possible even in areas with low output. If a low cooling power is required from the chamber side, the dedicated chiller can be used while the dual-purpose chiller can be stopped, thereby saving power. One dual-purpose chiller can cool multiple electrostatic chucks. This allows for a space-saving configuration.

[0010] Furthermore, the present invention (claim 2) is an invention of a cooling system, characterized in that, based on a control command for cooling sent from the control device, the dedicated chiller is operated prior to the dual-purpose chiller depending on the amount of output required for cooling contained in the control command, or the dual-purpose chiller is used to make up for any shortfall in output from the dedicated chiller.

[0011] When the cooling output is low, it can be operated only with the dedicated chiller. In this case, a dual-purpose chiller that does not require cooling does not require water cooling of the chiller itself, making it more efficient and saving power consumption. Also, because it is a small chiller, output adjustments can be made efficiently when the cooling output is low. Furthermore, by using the dual-purpose chiller to make up for any shortfall in the output of the dedicated chiller, overall power consumption can be reduced.

[0012] Furthermore, the present invention (claim 3) is a cooling system invention, characterized in that cooling by the dedicated chiller and the dual-purpose chiller is performed via a refrigerant, respectively, the control command of the control device includes a scheduled time for increasing or decreasing the cooling output, and cooling by at least one of the dedicated chiller and the dual-purpose chiller is performed by increasing or decreasing the cooling output by the delay time in consideration of the delay time until the refrigerant reaches the electrostatic chuck, prior to the scheduled time.

[0013] Taking into account the delay time until the coolant reaches the electrostatic chuck, the cooling output is increased or decreased by the delay time ahead of the scheduled time, thereby enabling cooling at an appropriate timing without delay for the electrostatic chuck, thereby improving the etching efficiency when etching a wafer in the chamber.

[0014] Furthermore, the present invention (Claim 4) is an invention of a cooling system, characterized in that it comprises a first pipe arranged between the dedicated chiller and the multiple chambers, and branch pipes having one end connected to the dual-purpose chiller and the other end connected to each of the multiple chambers, and valves are arranged on the branch pipes corresponding to the multiple chambers.

[0015] When the valve is closed, cooling of the electrostatic chuck in the closed chamber is not required, which reduces the load on the dual-purpose chiller and reduces the loss of water cooling and power for the chiller, improving utility.

[0016] Furthermore, the present invention (Claim 5) is an invention of a cooling system, characterized in that it comprises an airtight housing that houses the dedicated chiller and the dual-purpose chiller, the refrigerant is a gas, and the housing is equipped with a gas leak detector that detects leakage of the gas.

[0017] Compared to housing a large chiller, housing a small dedicated chiller and a dual-purpose chiller can save space. If the refrigerant is gas, there is a risk of fire or explosion if it leaks, depending on the composition. However, by housing the dedicated chiller and dual-purpose chiller in an airtight housing and equipping them with a gas leak detector, gas leaks can be detected accurately, allowing for quick response, such as preventing combustion in advance. In addition, since only one gas leak detector needs to be installed per housing, it is energy-efficient and inexpensive.

[0018] Furthermore, the present invention (claim 6) is a cooling system invention, which is configured to include at least one set of a first base connected to the dedicated chiller and a second base connected to the dual-purpose chiller below the electrostatic chuck.

[0019] At least one second base unit connected to a dual-purpose chiller is provided. If the output required for cooling increases, this can be easily accommodated by providing multiple combinations of dual-purpose chillers and second base units. [Effects of the Invention]

[0020] As described above, according to the present invention (claim 1), the dedicated chiller and the dual-purpose chiller are operated together based on a control command from the control device, making it possible to cover the maximum output required for cooling the electrostatic chuck, thereby enabling efficient operation even in areas with low cooling output. When a low cooling power is required from the chamber side, the dedicated chiller can be used while the dual-purpose chiller is stopped, thereby saving power. One dual-purpose chiller can cool multiple electrostatic chucks. This allows for a space-saving configuration. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a diagram illustrating a configuration of a cooling system according to an embodiment of the present invention. [Figure 2] Cooling system communication control diagram [Figure 3] FIG. 1 is a diagram illustrating a control method for a cooling system according to an embodiment of the present invention. [Figure 4]A diagram explaining the occurrence of delay time in the arrival of refrigerant gas due to the length of the gas piping. [Figure 5] Example of multiple chillers grouped together in a panel [Figure 6] Example of cooling structure for Cryo Etch DETAILED DESCRIPTION OF THE INVENTION

[0022] An embodiment of the present invention will be described below. A configuration diagram of this cooling system 10 is shown in Fig. 1. In Fig. 1, n chambers 1 are arranged, namely chamber 1A, chamber 1B, ... chamber 1N. An electrostatic chuck 3 (not shown) is arranged in each chamber 1, and a wafer is placed on this electrostatic chuck 3.

[0023] A base 11A1 having a gas passage formed therein is fixed to the lower surface of the electrostatic chuck 3 in the chamber 1A, and a base 11A2 having a similar gas passage formed therein is further fixed to the lower surface of the base 11A1. That is, the base 11 is configured by stacking the base 11A1 and the base 11A2 in two stages. However, the bases 11A1 and 11A2 may be combined into one base 11, and two gas passages may be formed inside the base 11.

[0024] One end of a gas pipe 15A is attached to the base 11A1, and a chiller 13A is attached to the other end of the gas pipe 15A. A refrigerant gas is supplied from the chiller 13A and passes through a gas passage inside the base 11A1, thereby cooling the base 11A1. Cooling the base 11A1 cools the electrostatic chuck 3, which in turn cools the wafer.

[0025] Similarly, a base 11B1 is fixed to the lower surface of the electrostatic chuck 3 in the chamber 1B, and a base 11B2 is further fixed to the lower surface of the base 11B1. One end of a gas pipe 15B is attached to the base 11B1, and the other end of the gas pipe 15B is attached to a chiller 13B. A refrigerant gas is supplied from the chiller 13B and passes through a gas passage inside the base 11B1, thereby cooling the base 11B1. Similarly, a base 11N1, a gas pipe 15N, and a chiller 13N are attached to the chamber 1N. The chillers 13A to 13N correspond to dedicated chillers, and the gas pipes 15A to 15N correspond to first pipes.

[0026] On the other hand, one end of a gas branch pipe 17A is attached to the base 11A2, and the other end of the gas branch pipe 17A is connected to a chiller 23 corresponding to a dual-purpose chiller via a gas junction pipe 21. A valve 19A is provided midway along the gas branch pipe 17A. Similarly, one end of a gas branch pipe 17B is attached to the base 11B2, and the other end of the gas branch pipe 17B is attached to a chiller 23 via a gas junction pipe 21. A valve 19B is provided midway along the gas branch pipe 17B. Similarly, a base 11N2, a gas pipe 17N, and a valve 19N are attached to the chamber 1N, and the chamber 1N is connected to a chiller 23 via a gas junction pipe 21.

[0027] Next, the control of the cooling system according to this embodiment will be described with reference to FIG. FIG. 2 shows a communication control diagram of the cooling system. In FIG. 2, signals can be transmitted between the chamber 1, the vacuum pump 5, the chiller 13, the chiller 23, and the radio frequency (RF) power source 9. The signals are transmitted, for example, via EtherCAT (registered trademark). These signals include the temperature near the electrostatic chuck 3 and the magnitude of the radio frequency (RF) power source 9 required for plasma processing. The chiller control device 30 controls the chillers 13A to 13N, the chiller 23, and the valves 19A to 19N used in plasma processing based on the temperature near the electrostatic chuck 3 and the magnitude of the radio frequency (RF) power source 9.

[0028] Next, a control method for the cooling system according to this embodiment will be described with reference to FIGS. 3A shows a time chart of an example of changes in the magnitude of the radio frequency (RF) power 9 required in an etching process schedule. A first level of power is required from the chamber 1 at time t1, a second level of power is required at time t3, and the power requirement is released at time t5. Heat is generated near the electrostatic chuck 3 in accordance with this level of power.

[0029] Figure 3(B) shows a time chart of chiller power consumption when cooling is performed using a single large chiller in relation to the required power. The characteristics of Figure 3(B) basically change the chiller's cooling capacity in accordance with changes in the amount of power required in Figure 3(A). In this case, the maximum power required by the chiller is assumed to be 10 kW.

[0030] 4, if the gas pipe 15 between the chamber 1 and the chiller 13 is long, it takes time for the cooling gas supplied from the chiller 13 to reach the chamber 1. For example, if the length of the gas pipe 15 is 10 m, a delay of about 20 seconds may occur. Under such circumstances, if the refrigerant gas is supplied after the temperature of the wafer surface has risen, there is a risk that the wafer temperature will rise even further.

[0031] On the other hand, the scheduled time for application of the radio frequency (RF) power 9 is known in the schedule for chamber 1. Therefore, in the characteristics shown in FIG. 3B, control is performed by advancing this delay time (t = 20 seconds). That is, the chiller control device 30 sends a control command to start cooling at time t0, which is earlier than the cooling start command time t1 by the delay time t. Similarly, control commands are sent for times t3 and t5 at times t2 and t4, which are earlier by the delay time t. This enables fine-tuned control so that the wafer surface temperature is appropriate when the power supply from the radio frequency (RF) power 9 increases. Note that in FIG. 3B, the chiller supplies standby operation output before time t0 and after time t4. On the other hand, if the gas pipe 15 between the chamber 1 and the chiller 13 is short, the delay time t will be approximately 0 seconds, and therefore cooling can be performed with sufficient precision without having to perform control that advances the delay time.

[0032] Figure 3(C) shows in a time chart how the amount of power required for radio frequency (RF) power 9 can be covered by operating both the dedicated chiller 13 and the dual-purpose chiller 23. The upper diagram in Figure 3(C) shows the change in cooling capacity when operating a chiller 13 with a maximum cooling capacity of 6 kW. If the chillers 13 continue to operate according to the etching processing schedule, only one chiller 13 needs to be operated until time t2. This allows for efficient and energy-saving operation.

[0033] If only the chiller 13 is operated between time t2 and time t4, it would be impossible to supply a cooling output exceeding 6 kW. At this time, the chiller control device 30 issues a control command to open the valve 19 and operate the chiller 23 between time t2 and time t4, thereby making up for the 4 kW shortage in the cooling capacity of the chiller 13. As for the operation of the chiller 23, the 4 kW shortage in cooling capacity at time t2 can be predicted in advance, so operation can be started in advance so that the necessary cooling capacity can be immediately provided before the valve 19 is switched. This improves cooling efficiency. Only the valves 19A-19N corresponding to the chambers 1A-1N with insufficient cooling capacity need to be opened, which saves power.

[0034] Furthermore, a small pump is used to operate the 6kW chiller 13, which is more efficient and consumes less power when operating in areas with low cooling capacity compared to when a 10kW pump is operated. Operation of areas with low cooling capacity can be handled by operating only this chiller 13, while chiller 23 is stopped. As only one chiller 13 is operating, power consumption is low.

[0035] Furthermore, chiller 13 uses a small pump and has low maximum power consumption, so the amount of cooling water required to cool the chiller is small. Furthermore, only when the cooling capacity is insufficient is valve 19A-19N opened to start operation of chiller 23, thereby compensating for the lack of cooling capacity of chiller 13, thereby saving power. Chiller 13 can be configured to be small, and chiller 23 can be used for multiple purposes, so it can be configured to save space. Furthermore, chiller 13 takes less time to reach rated speed than large chillers, and cooling output can be increased or decreased quickly. As described above, by lowering the temperature of the electrostatic chuck 3 using the dedicated chiller 13 and the dual-purpose chiller 23, it is possible to reduce the wafer temperature while suppressing power consumption, and to maintain a high etching rate.

[0036] Figure 5 shows an example in which chillers 13 and 23 are integrated into a panel. With global warming becoming more prevalent these days and stricter regulations on fluorocarbons being put in place to combat this, it is desirable to use environmentally friendly non-fluorocarbon gas as the refrigerant gas for chillers 13 and 23. Depending on the composition of this non-fluorocarbon gas, it may be flammable and pose a risk if it leaks, so it is desirable to have a gas leak detection system. While the outer frame of the panel is omitted in Figure 5, it is constructed with a highly airtight housing. This means that only one gas leak detector 31 is required, saving space and power. Although a refrigerant gas is used as the refrigerant in this embodiment, a liquid refrigerant may also be used. Also, cooling by a Peltier element in the cooling portion of the electrostatic chuck without using a refrigerant is also applicable. It should be noted that the present invention can be modified and combined in various ways without departing from the spirit of the present invention, and it goes without saying that the present invention also covers such modifications and combinations. [Explanation of symbols]

[0037] 1 chamber 3 Electrostatic Chuck 5. Vacuum pump 7 Process gases 9 Radio frequency (RF) power 10 Cooling System 11 Foundation 13 Chiller (dedicated) 15 Gas piping 17 Gas branch piping 19 Valve 21 Gas junction piping 23 Chiller (dual use) 30 Chiller control device 31 Gas leak detector

Claims

1. an electrostatic chuck disposed in each of the plurality of chambers; dedicated chillers provided corresponding to the plurality of chambers, respectively, for cooling the electrostatic chuck; a dual-purpose chiller that cools the electrostatic chucks of the plurality of chambers; a control device for controlling operation of the plurality of chambers; a cooling system capable of covering a maximum output required for cooling the electrostatic chuck by operating the dedicated chiller and the dual-purpose chiller together based on a control command from the control device.

2. The cooling system of claim 1, characterized in that, based on a control command for cooling sent from the control device, the dedicated chiller is operated prior to the dual-purpose chiller, or the dual-purpose chiller is used to make up for any shortfall in output from the dedicated chiller, depending on the amount of output required for cooling contained in the control command.

3. The cooling by the dedicated chiller and the dual-purpose chiller is performed via a refrigerant, The control command of the control device includes a scheduled time for increasing or decreasing the cooling output, 3. The cooling system according to claim 1, wherein the cooling output of at least one of the dedicated chiller and the dual-purpose chiller is increased or decreased by the delay time before the scheduled time, taking into account a delay time required for the coolant to reach the electrostatic chuck.

4. a first pipe disposed between the dedicated chiller and the plurality of chambers; one end of the branch pipe connected to the dual-purpose chiller and the other end of the branch pipe connected to each of the plurality of chambers; 3. The cooling system according to claim 1, wherein the branch pipes are provided with valves corresponding to the plurality of chambers.

5. an airtight housing that houses the dedicated chiller and the dual-purpose chiller; 4. The cooling system according to claim 3, wherein the refrigerant is a gas, and the housing is provided with a gas leak detector for detecting leakage of the gas.

6. a first base connected to the dedicated chiller below the electrostatic chuck; 3. The cooling system according to claim 1, further comprising at least one second base connected to the dual-purpose chiller.

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