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 particularly to a cooling system that can efficiently cool an electrostatic chuck in a power-saving and space-saving manner when processing a semiconductor wafer.

Background Art

[0002] Recently, the highly informationized society has been developing, and an increase in the number of memory layers and higher processing accuracy have been demanded. Against this background, when processing semiconductor wafers such as silicon, plasma processing by plasma etching is widely performed. In plasma etching, even when the surface of the wafer is deeply etched by plasma processing, the etching rate can be increased by cooling the wafer that becomes hot. In particular, recently, an insulating film etching technology (Cryo Etch) performed in the ultra-low temperature region has attracted attention. According to this Cryo Etch, it is said to be an epoch-making technology that can significantly increase the etching rate and greatly reduce the global warming potential. And in order to realize this Cryo Etch, plasma processing is performed by bringing a wafer into close contact with the holding surface of a chuck table having a cooling structure.

[0003] An example of the cooling structure of Cryo Etch will be described with reference to FIG. 6. In FIG. 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 adsorbed by an electric force by this electrostatic chuck 3. The inside of the chamber 1 is evacuated by a vacuum pump 5 or a process gas 7 is introduced based on the semiconductor processing schedule. Then, high-frequency (RF) power 9 is applied to generate plasma in the chamber 1.

[0004] When the temperature of the wafer rises during plasma processing, the etching rate decreases. Therefore, a base 11 with a gas passage for passing a refrigerant gas inside is disposed on the lower surface of the electrostatic chuck 3, and the refrigerant gas is supplied from a chiller 13 to the base 11 (see, for example, Patent Document 1). The chiller 13 itself is cooled by, for example, water cooling. In addition, in order to increase the etching rate, the power consumption of the high-frequency (RF) power 9 also tends to increase. For this reason, the amount of heat generated due to the increase in power further increases, and further heat dissipation and control by the chiller 13 are required. From such a situation, the cooling capacity required for the chiller gradually increases, and a large chiller is tended to be demanded.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, when the chiller is enlarged, although the operation near the rated output is configured to be highly efficient, in the operation at an output lower than the rated output, the lower the output of the refrigerant gas, the more rapidly the operation efficiency drops. For this reason, there is a risk of utility degradation such as power loss or the need for extra cooling water to cool the chiller according to the loss. In addition, when the chiller is enlarged, the required capacity of the cooling water of the chiller is also greatly demanded, and the installation space may also increase.

[0007] The present invention has been made in view of such conventional problems, and an object thereof is to provide a cooling system capable of efficiently cooling an electrostatic chuck with power saving and space saving when processing a semiconductor wafer.

Means for Solving the Problems

[0008] Therefore, the present invention (Claim 1) is an invention of a cooling system, comprising electrostatic chucks respectively disposed in a plurality of chambers, dedicated chillers respectively disposed corresponding to the plurality of chambers for cooling the electrostatic chucks, a shared chiller for cooling the electrostatic chucks of the plurality of chambers with one unit, and a control device for controlling the operation of the plurality of chambers, and by operating the dedicated chiller and the shared chiller together based on a control command from the control device, it is characterized in that the maximum output required for cooling the electrostatic chuck can be covered.

[0009] When covering the maximum output required for cooling the electrostatic chuck with one large chiller, there is a risk that the cooling efficiency will deteriorate in the part with low output. However, by operating the dedicated chiller and the shared chiller together, efficient operation can be achieved even in the part with low output. When a low cooling power is required from the chamber side, the shared chiller can be stopped while coping with it with the dedicated chiller, so it is power-saving. The shared chiller cools a plurality of electrostatic chucks with one unit. Therefore, it can be configured to save space.

[0010] Further, the present invention (Claim 2) is an invention of a cooling system, characterized in that based on a cooling control command sent from the control device, according to the magnitude of the output required for cooling included in the control command, the dedicated chiller is operated prior to the shared chiller, or the shortage of the output of the dedicated chiller is supplemented by the shared chiller for operation.

[0011] When the cooling output is small, it can be operated only with the dedicated chiller. In this case, in the shared chiller that does not require cooling, it is not necessary to perform water cooling or the like on the chiller itself, so the efficiency is good and power consumption can be saved. Also, the output adjustment when the cooling output is small can be efficiently performed because it is a small chiller. Furthermore, by supplementing the shortage of the output of the dedicated chiller with the shared chiller, power can be saved as a whole.

[0012] Furthermore, the present invention (Claim 3) is an invention of a cooling system, wherein the cooling by the dedicated chiller and the combined chiller is each performed via a refrigerant, and the control command of the control device includes a scheduled time for increasing or decreasing the output for cooling. Cooling by at least one of the dedicated chiller and the combined chiller is performed by increasing or decreasing the output for cooling by the delay time in advance of the scheduled time in consideration of the delay time until the refrigerant reaches the electrostatic chuck.

[0013] In consideration of the delay time until the refrigerant reaches the electrostatic chuck, the output for cooling is increased or decreased by the delay time in advance of the scheduled time. For this reason, cooling can be performed at an appropriate timing without delay with respect to the electrostatic chuck. For this reason, when etching a wafer in the chamber, the etching efficiency can be increased.

[0014] Furthermore, the present invention (Claim 4) is an invention of a cooling system, comprising a first pipe disposed between the dedicated chiller and the plurality of chambers, and a branch pipe having one end connected to the combined chiller and the other end connected to each of the plurality of chambers, wherein valves are disposed in the branch pipe corresponding to the plurality of chambers.

[0015] When the valve is closed, it is not necessary to cool the electrostatic chuck of the closed chamber. For this reason, the burden on the combined chiller is reduced accordingly, and the water cooling and power loss of the chiller can be reduced, improving the utility.

[0016] Furthermore, the present invention (Claim 5) is an invention of a cooling system, comprising an airtight housing for housing the dedicated chiller and the combined chiller, wherein the refrigerant is a gas, and the housing is provided with a gas leak detector for detecting that the gas has leaked.

[0017] When storing a large chiller, the storage of small dedicated chillers and combined-use chillers can be configured to save space. When the refrigerant is a gas, depending on its components, there is a risk of combustion or explosion when it leaks. However, by storing the dedicated chiller and the combined-use chiller in an airtight housing and equipping it with a gas leak detector, gas leaks can be accurately detected, and prompt responses such as preventing combustion in advance can be made. Also, since only one gas leak detector needs to be installed for the housing, it is power-saving and inexpensive.

[0018] Furthermore, the present invention (claim 6) is an invention of a cooling system, and at least one set of a first base connected to the dedicated chiller and a second base connected to the combined-use chiller is provided below the electrostatic chuck.

[0019] It is provided with at least one set of a second base connected to the combined-use chiller. When the output required for cooling increases, it can be easily dealt with by providing a plurality of sets of the combination of the combined-use chiller and the second base.

Effect of the Invention

[0020] As described above, according to the present invention (claim 1), by operating the dedicated chiller and the combined-use chiller together based on a control command from the control device, it is configured to cover the maximum output required for cooling the electrostatic chuck. Therefore, efficient operation can be achieved even in the part where the cooling output is low. When a low cooling power is required from the chamber side, the combined-use chiller can be stopped while dealing with it with the dedicated chiller, so it is power-saving. The combined-use chiller cools a plurality of electrostatic chucks with one unit. For this reason, it can be configured to save space.

Brief Explanation of Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0022] Hereinafter, embodiments of the present invention will be described. A configuration diagram of this cooling system 10 is shown in FIG. 1. In FIG. 1, n chambers 1A, 1B,... 1N are arranged in the chamber 1. 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 with a gas passage formed is fixed to the lower surface of the electrostatic chuck 3 in the chamber 1A, and further, a base 11A2 with a gas passage formed is fixed to the lower surface of this base 11A1. That is, the base 11 is configured by stacking the base 11A1 and the base 11A2 in two stages. However, the base 11A1 and the base 11A2 may be combined into one as the base 11, and two systems of gas passages may coexist inside this 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. Refrigerant gas is supplied from the chiller 13A and passes through the gas passage inside the base 11A1 to cool the base 11A1. And when this base 11A1 is cooled, the electrostatic chuck 3 is cooled, and the wafer can be cooled.

[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 this base 11B1. One end of a gas pipe 15B is attached to the base 11B1, and a chiller 13B is attached to the other end of the gas pipe 15B. Refrigerant gas is supplied from the chiller 13B and passes through the gas passage inside the base 11B1 to cool the base 11B1. Furthermore, similarly for the chamber 1N, a base 11N1, a gas pipe 15N, and a chiller 13N are attached. The chillers 13A to 13N correspond to dedicated chillers, and the gas pipes 15A to 15N correspond to the 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 shared chiller via a gas confluence pipe 21. A valve 19A is disposed in the middle of 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 has the chiller 23 attached via the gas confluence pipe 21. A valve 19B is disposed in the middle of the gas branch pipe 17B. Furthermore, similarly for the chamber 1N, a base 11N2, a gas pipe 17N, and a valve 19N are attached and are connected to the chiller 23 via the gas confluence pipe 21.

[0027] Next, based on FIG. 2, the control of the cooling system according to this embodiment will be described. FIG. 2 shows a communication control system diagram of the cooling system. In FIG. 2, signals can be transmitted between the chamber 1, the vacuum pump 5, the chillers 13, the chiller 23, and the high-frequency (RF) power 9. The signal transmission is performed by communication using, for example, EtherCAT (registered trademark). This signal also includes the temperature near the electrostatic chuck 3 and the magnitude of the high-frequency (RF) power 9 required in plasma processing. The chiller control device 30 controls the chillers 13A to 13N, the chiller 23, and the valves 19A to 19N in plasma processing based on the temperature near the electrostatic chuck 3 and the magnitude of the high-frequency (RF) power 9.

[0028] Next, a control method for the cooling system according to the present embodiment will be described with reference to FIGS. 3 and 4. FIG. 3(A) shows, in a time chart, an example of changes in the magnitude of the power required for high-frequency (RF) power 9 in the etching process schedule. From chamber 1, power of the first-stage magnitude is required at time t1, power of the second-stage magnitude is required at time t3, and the power requirement is released at time t5. Along with this magnitude of power, heat is generated near the electrostatic chuck 3.

[0029] FIG. 3(B) shows a time chart of the chiller power when cooling is performed by one large chiller for the required power. As a characteristic of FIG. 3(B), basically, the magnitude of the cooling capacity of the chiller changes in accordance with the change in the magnitude of the power required in FIG. 3(A). At this time, it is assumed that the maximum required power for the chiller is 10 kW.

[0030] Here, as shown in FIG. 4, when 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 accordingly. For example, when the length of the gas pipe 15 is 10 m, a delay time of about 20 seconds may occur. Under such circumstances, in the method of supplying the refrigerant gas after the temperature of the wafer surface has risen, there is a risk that the temperature of the wafer will rise further.

[0031] On one hand, in the schedule on the chamber 1 side, the scheduled time for applying the high-frequency (RF) power 9 is known. Therefore, in the characteristics of Fig. 3(B), control is performed by advancing this delay time (t = 20 seconds). That is, from the chiller control device 30, a control command is sent to start cooling at time t0, which is the start command time t1 of cooling advanced by the delay time t. Similarly, control commands are sent to times t2 and t4, which are times t3 and t5 advanced by the delay time t, respectively. Thereby, fine control becomes possible so that the temperature on the surface of the wafer becomes appropriate when the power supply from the high-frequency (RF) power 9 increases. In Fig. 3(B), before time t0 and after time t4, the output during standby operation is supplied from the chiller. On the other hand, if the gas pipe 15 between the chamber 1 and the chiller 13 is temporarily short, the delay time t becomes approximately 0 seconds. Therefore, cooling can be handled with sufficient accuracy without performing control by advancing the delay time.

[0032] Fig. 3(C) shows, in a time chart, a method of covering the magnitude of the power required for the high-frequency (RF) power 9 by operating both the dedicated chiller 13 and the shared chiller 23. The upper diagram in Fig. 3(C) shows the change in the cooling capacity when the chiller 13 with a maximum cooling capacity of 6 kW that can be output is operated. If the chiller 13 is continuously operated according to the etching process schedule, only one operation of the chiller 13 is required until time t2. Therefore, it can be efficiently operated with power saving.

[0033] During the operation of only the chiller 13 from time t2 to time t4, a cooling output exceeding 6 kW cannot be supplied. At this time, the chiller control device 30 issues a control command to open the valve 19 and operate the chiller 23 from time t2 to time t4, thereby compensating for the 4-kW shortage in the cooling capacity of the chiller 13. Regarding the operation of the chiller 23, since the 4-kW shortage in the cooling capacity at time t2 can be predicted in advance, the operation can be started in advance so that the necessary cooling capacity can be immediately provided before the switching of the valve 19. Therefore, the cooling efficiency can be increased. It is only necessary to open the valves 19A to 19N corresponding to the chambers 1A to 1N with insufficient cooling capacity. For this reason, it is power-saving.

[0034] Also, a small pump is used for the operation of the 6-kW chiller 13. Compared with the case of operating a 10-kW pump, the operation of the part with low cooling capacity is more efficient and consumes less power. The operation of the part with low cooling capacity can be handled only by the operation of this chiller 13, and the chiller 23 is stopped. Since only one chiller 13 is operating, the power consumption is small.

[0035] Furthermore, in the chiller 13, a small pump is used and the maximum power consumption is also low, so the amount of cooling water required for cooling the chiller can be reduced. Furthermore, it is power-saving because it is only necessary to open the valves 19A to 19N and start the operation of the chiller 23 only when the cooling capacity is insufficient to compensate for the shortage in the cooling capacity of the chiller 13. The chiller 13 can be configured to be small, and the chiller 23 can be used concurrently, so it can be configured to save space. Furthermore, in the chiller 13, the time to reach the rated speed is shorter than that of a large chiller, and the increase and decrease of the cooling output can be performed quickly. As described above, by lowering the temperature of the electrostatic chuck 3 with the dedicated chiller 13 and the concurrent chiller 23, it is possible to lower the temperature of the wafer while suppressing the power consumption, and maintain a high etching rate.

[0036] An example in which these chillers 13 and 23 are collectively configured within a panel is shown in FIG. 5. Here, with global warming progressing in recent years and regulations on chlorofluorocarbons becoming stricter as a countermeasure, it is desirable to apply an environmentally friendly non-chlorofluorocarbon gas as the refrigerant gas for chillers 13 and 23. Depending on the composition of this non-chlorofluorocarbon gas, there is a risk of danger if it is flammable and leaks, so it is desirable to detect gas leaks. In FIG. 5, although the outer frame of the panel is omitted in the figure, it is configured with a highly airtight housing. For this reason, only one gas leak detector 31 needs to be arranged, saving space and power. In this embodiment, a refrigerant gas is used as the refrigerant, but for example, a liquid refrigerant may also be used. Further, cooling by a Peltier element can also be applied to the cooling part of the electrostatic chuck without using a refrigerant. Note that the present invention can be variously modified and combined without departing from the spirit of the present invention, and it is natural that the present invention also extends to such modified and combined things.

Explanation of Signs

[0037] 1 Chamber 3 Electrostatic chuck 5 Vacuum pump 7 Process gas 9 High-frequency (RF) power 10 Cooling system 11 Base 13 Chiller (dedicated) 15 Gas pipe 17 Gas branch pipe 19 Valve 21 Gas confluence pipe 23 Chiller (combined use) 30 Chiller control device 31 Gas leak detector

Claims

1. Electrostatic chucks respectively disposed in a plurality of chambers, Dedicated chillers respectively disposed corresponding to the plurality of chambers for cooling the electrostatic chucks, A combined chiller for cooling the electrostatic chucks of the plurality of chambers with a single unit, A control device for controlling the operation of the plurality of chambers, A cooling system characterized in that by operating the dedicated chiller and the combined chiller together based on a control command from the control device, the maximum output required for cooling the electrostatic chuck can be covered.

2. Based on a cooling control command sent from the control device, according to the magnitude of the output required for cooling included in the control command, the dedicated chiller is operated prior to the combined chiller, or the shortage of the output of the dedicated chiller is supplemented by the combined chiller for operation. The cooling system according to Claim 1.

3. Cooling by the dedicated chiller and the combined chiller is respectively performed via a refrigerant, The control command of the control device includes a scheduled time for increasing or decreasing the output for cooling, Cooling by at least one of the dedicated chiller and the combined chiller is performed by increasing or decreasing the output for cooling in advance by the delay time from the scheduled time in consideration of the delay time until the refrigerant reaches the electrostatic chuck. The cooling system according to Claim 1 or Claim 2.

4. A first pipe disposed between the dedicated chiller and the plurality of chambers, A branch pipe having one end connected to the combined chiller and the other end respectively connected to the plurality of chambers, characterized in that valves are disposed in the branch pipe corresponding to the plurality of chambers. The cooling system according to Claim 1 or Claim 2.

5. An airtight housing for housing the dedicated chiller and the combined chiller, The refrigerant is a gas, and the housing is provided with a gas leak detector for detecting that the gas has leaked. The cooling system according to Claim 3.

6. At least one set of a first base connected to the dedicated chiller and a second base connected to the combined chiller is provided below the electrostatic chuck. The cooling system according to Claim 1 or Claim 2.

7. The cooling system according to any one of Claims 1 to 6, further comprising a display device for displaying an operation state of the cooling system.

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