Temperature control system

Abstract

This system provides a temperature control mechanism that allows for efficient and uniform cooling of electrostatic chucks during semiconductor wafer processing, with minimal power consumption, and facilitates easy temperature management. [Solution] The electrostatic chuck 3 is disposed in a chamber 1, and a first chiller and a second chiller are provided to cool the electrostatic chuck 3. The base 11 at the bottom of the electrostatic chuck 3 has a first flow path through which a first temperature-regulating medium from the first chiller flows, and a second flow path through which a second temperature-regulating medium from the second chiller flows. In the first flow path, the first temperature-regulating medium flows in from the outer circumference side of the base and is discharged from the inner circumference side, while in the second flow path, the second temperature-regulating medium flows in from the inner circumference side of the base and is discharged from the outer circumference side, thereby controlling the temperature on the electrostatic chuck 3.

Description

Technical Field

[0001] The present invention relates to a temperature adjustment system, and particularly to a temperature adjustment system that can efficiently and uniformly cool an electrostatic chuck with power saving during the processing of a semiconductor wafer, and is easy to manage temperature.

Background Art

[0002] Recently, with the progress of the highly informationized society, an increase in the stacking number of memories and higher precision in processing accuracy are required. Against this background, when processing a semiconductor wafer 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 technique (Cryo Etch) performed in an extremely low temperature region has attracted attention. According to this Cryo Etch, it is said to be an epoch-making technique 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 closely adhering a wafer to the holding surface of a chuck table having a cooling structure.

[0003] An example of the cooling structure of Cryo Etch will be described based on FIG. 5. In FIG. 5, 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] During plasma processing, the etching rate decreases when the wafer temperature rises. Therefore, a base 11 with a gas passage formed inside for circulating refrigerant gas is provided on the lower surface of the electrostatic chuck 3, and refrigerant gas is supplied to this base 11 from the chiller 13 (see, for example, Patent Document 1). The chiller 13 itself is cooled, for example, by water cooling.

[0005] Furthermore, in order to increase the etching rate, the power consumption of the radio frequency (RF) power 9 also tends to increase. As a result, the amount of heat generated by the increased power also increases further, requiring even greater heat dissipation and control by the chiller 13. Given these circumstances, the cooling capacity required of chillers is gradually increasing, and there is a growing demand for larger chillers. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-36899 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] By the way, when increasing the size of a chiller, it is necessary to operate this large chiller even when operating at an output lower than the rated output. In this case, while operation near the rated output is configured to be highly efficient, when operating at an output lower than the rated output, the operating efficiency drops sharply as the refrigerant gas output decreases. Therefore, it may not be possible to save energy.

[0008] Furthermore, in operation with such a large chiller, the temperature difference between the input of refrigerant gas to the base 11 and the output from the base 11 is large, which may make it difficult to partially control the temperature on the electrostatic chuck 3.

[0009] This invention has been made in view of the above-mentioned conventional problems, and aims to provide a temperature control system that allows for efficient and uniform cooling of an electrostatic chuck with low power consumption and facilitates temperature control when processing semiconductor wafers. [Means for solving the problem]

[0010] Therefore, the present invention (Claim 1) is an invention of a temperature control system comprising an electrostatic chuck disposed in a chamber, a first chiller and a second chiller for cooling the electrostatic chuck, wherein a first flow path through which a first temperature control medium from the first chiller flows and a second flow path through which a second temperature control medium from the second chiller flows are formed in the base at the bottom of the electrostatic chuck, wherein in the first flow path the first temperature control medium flows in from the outer circumference side of the base and is discharged from the inner circumference side, and in the second flow path the second temperature control medium flows in from the inner circumference side of the base and is discharged from the outer circumference side, thereby controlling the temperature on the electrostatic chuck.

[0011] By configuring multiple chillers, good operating efficiency can be maintained even when operating at low chiller output. In the first channel, the first temperature-regulating medium flows in from the outer circumference of the base and is discharged from the inner circumference, while in the second channel, the second temperature-regulating medium flows in from the inner circumference of the base and is discharged from the outer circumference, thereby making the temperature distribution on the electrostatic chuck nearly uniform.

[0012] Furthermore, the present invention (claim 2) is an invention of a temperature control system, characterized in that the first flow path and the second flow path are formed in a spiral shape.

[0013] The spiral shape allows for a longer flow path in contact with the base, resulting in a higher cooling effect. Therefore, the base temperature can be uniformly cooled at any point.

[0014] Furthermore, the present invention (claim 3) is an invention of a temperature control system, characterized in that the first channel and the second channel are composed of a multi-layer structure of two or more layers.

[0015] The multi-layer structure allows for efficient temperature reduction of the base. Structures with three or more layers can be easily created by stacking the layers. By optimizing the flow of the temperature-regulating medium through each layer, a uniform temperature distribution can be achieved on the base.

[0016] Furthermore, the present invention (claim 4) is a temperature control system characterized in that the timing of inflow of the first temperature control medium and the second temperature control medium and the flow rate per unit time are the same.

[0017] By making the timing and flow rate per unit time of the inflow of the first temperature-regulating medium and the second temperature-regulating medium the same, the temperature distribution of the base can be made uniform.

[0018] Furthermore, the present invention (claim 5) is a temperature control system invention characterized by stopping either the first chiller or the second chiller and operating only the other chiller.

[0019] Since only one of multiple chillers can be used for operation, energy savings can be achieved.

[0020] Furthermore, the present invention (claim 6) is an invention of a temperature control system, characterized in that it comprises a heating means capable of heating the base at least partially.

[0021] Since the temperature distribution can be corrected by the heating method, it is easy to further equalize the temperature distribution of the base. [Effects of the Invention]

[0022] As described above, according to the present invention (Claim 1), in the first flow path, the first temperature-regulating medium flows in from the outer circumference side of the base and is discharged from the inner circumference side, while in the second flow path, the second temperature-regulating medium flows in from the inner circumference side of the base and is discharged from the outer circumference side, thereby making the temperature distribution on the electrostatic chuck substantially uniform. [Brief explanation of the drawing]

[0023] [Figure 1] Configuration diagram of the temperature control system according to an embodiment of the present invention [Figure 2] Configuration diagram of the temperature control system according to another embodiment of the present invention [Figure 3] Example of a temperature correction device for performing temperature correction by a heater [Figure 4] Diagram showing an example of the arrangement of the temperature correction device [Figure 5] Example of the cooling structure of Cryo Etch

Embodiments for Carrying Out the Invention

[0024] Hereinafter, embodiments of the present invention will be described. A configuration diagram of this temperature control system 10 is shown in FIG. 1. Note that the same reference numerals are given to the same elements as those in FIG. 5, and the description thereof is omitted. FIG. 1(A) shows a plan view of a piping structure disposed inside the base 11, and FIG. 1(B) shows a cross-sectional view (side view) taken along the line A-A in FIG. 1(A).

[0025] Below the electrostatic chuck 3, the upper base portion 11A and the lower base portion 11B are stacked in two layers. However, it may be configured with three or more layers. A pipe 21 corresponding to the first flow path is embedded in the upper base portion 11A. And this pipe 21 is wound in a spiral shape in the clockwise direction. The pipe diameters of the portions of the pipe 21 wound in a spiral shape are the same, and the radial intervals between adjacent pipes of the wound pipes are arranged to be equal. Then, a refrigerant gas 22 corresponding to the first temperature adjustment medium flows into a pipe inlet 21a of the pipe 21 formed on the outer peripheral side, and this refrigerant gas 22 is discharged from a pipe outlet 21b formed on the inner peripheral side.

[0026] Here, in recent years, global warming has been progressing, and regulations on fluorocarbons have become stricter as a countermeasure. Therefore, it is desirable to apply an environmentally friendly non-fluorocarbon gas as the refrigerant gas. Further, the refrigerant gas may be, for example, a liquid refrigerant.

[0027] Meanwhile, a pipe 23 corresponding to the second flow path is embedded in the lower part 11B of the base, and this pipe 23 is also arranged in a spiral shape in a clockwise direction. The diameter of the spiral-shaped portion of the pipe 23 is the same, and the radial spacing between adjacent pipes in the spiral is equal. A refrigerant gas 24 corresponding to the second temperature control medium flows into the pipe inlet 23a formed on the inner circumference of this pipe 23, and this refrigerant gas 24 is discharged from the pipe outlet 23b formed on the outer circumference.

[0028] The area of ​​the upper part 11A of the base and the area of ​​the lower part 11B of the base are the same, and the diameters of pipes 21 and 23 are the same. The number of spiral turns is also identical. The pipe inlet 21a and pipe outlet 23b are positioned 180 degrees apart. The inlet pipe 25 connected to the pipe inlet 21a is configured to penetrate the lower base layer 11B. Similarly, the discharge pipe 27 connected to the pipe outlet 21b is also configured to penetrate the lower base layer 11B.

[0029] Meanwhile, an inlet pipe 29 is connected to the pipe inlet 23a, and a discharge pipe 31 is connected to the pipe outlet 23b. The discharge pipe 27 and the inlet pipe 29 are positioned slightly offset from each other so that they do not overlap.

[0030] Although not shown in the diagram, for example, two chillers 13 are installed, with one of them connected to the inlet pipe 25 and the discharge pipe 27. The other chiller is connected to the inlet pipe 29 and the discharge pipe 31. It is desirable that each chiller 13 has sufficient capacity to cool the electrostatic chuck 3, even if only one is installed.

[0031] In this configuration, refrigerant gas 22 flows through the upper part 11A of the base via the piping 21. Since the refrigerant gas 22 absorbs heat from the electrostatic chuck 3, the temperature of the refrigerant gas at the piping inlet 21a, which is on the outer circumference side, is low, and the temperature at the piping outlet 21b, which is on the inner circumference side, is high. Therefore, if only the first flow path is used, the temperature of the refrigerant gas in the flow path will become high, changing the cooling performance and easily creating a temperature distribution.

[0032] Meanwhile, refrigerant gas 24 flows through the lower part 11B of the base via piping 23. Since the refrigerant gas 24 absorbs heat from the electrostatic chuck 3, the temperature of the refrigerant gas at the piping inlet 23a, which is on the inner circumference side, is low, and the temperature at the piping outlet 23b, which is on the outer circumference side, is high. By reversing the flow in the first and second channels in this way, the temperature of the piping section where piping 21 and piping 23 are combined becomes almost the same at any point within the plane of the electrostatic chuck 3. Therefore, by simultaneously introducing refrigerant gas into the first and second channels, the temperature distribution of the entire electrostatic chuck 3 can be made uniform. Furthermore, the flow directions of the first and second channels can also be configured in the opposite direction to that described above. Furthermore, by configuring multiple chillers, good operating efficiency can be maintained even when operating at low chiller output.

[0033] Next, another embodiment of the present invention will be described. In the above embodiment, the base was configured as a two-layer structure consisting of an upper base portion 11A and a lower base portion 11B, but another embodiment is one in which it is constructed as a single layer. Figure 2 shows a diagram of the temperature control system 20. Components identical to those in Figure 1 are given the same reference numerals and their descriptions are omitted. In Figure 2, piping 21 is installed on the base 33. This piping 21 is configured in the same way as in Figure 1.

[0034] Meanwhile, in the radial gaps between adjacent pipes in the pipe 21 around which the pipe 21 is wound, another pipe 41, corresponding to a second flow path, is wound in a spiral shape. This pipe 41 is also arranged in a clockwise spiral shape. The pipe inlet 41a of pipe 41 is located on the inner circumference so as to be adjacent to the pipe outlet 21b. The pipe outlet 41b is located on the outer circumference, similar to the pipe inlet 21a, and is positioned 180 degrees away from the pipe inlet 21a.

[0035] The diameter of the spirally wound portion of the pipe 41 is the same, and the radial spacing between adjacent pipes in the spiral is equal. A refrigerant gas 24, which corresponds to the second temperature control medium, flows into the pipe inlet 41a formed on the inner circumference of the pipe 41, and this refrigerant gas 24 is discharged from the pipe outlet 41b formed on the outer circumference.

[0036] In this configuration, refrigerant gas 22 flows through piping 21. Since the refrigerant gas 22 absorbs heat from the electrostatic chuck 3, the temperature of the refrigerant gas at the piping inlet 21a, which is on the outer circumference, is low, while the temperature at the piping outlet 21b, which is on the inner circumference, is high. Therefore, if only the first flow path is used, the temperature of the refrigerant gas in the flow path will become high, changing the cooling performance and easily creating a temperature distribution.

[0037] Meanwhile, refrigerant gas 24 flows through piping 41. Since the refrigerant gas 24 absorbs heat from the electrostatic chuck 3, the temperature of the refrigerant gas at the piping inlet 41a, which is on the inner circumference side, is low, and the temperature at the piping outlet 41b, which is on the outer circumference side, is high. By reversing the flow in the first and second channels in this way, the temperature of the piping section where piping 21 and piping 41 are combined becomes almost the same at any point within the plane of the electrostatic chuck 3. Therefore, by simultaneously introducing refrigerant gas into the first and second channels, the temperature distribution of the entire electrostatic chuck 3 can be made uniform.

[0038] Next, we will explain how to control the temperature distribution on the electrostatic chuck with greater precision. In the preliminary evaluation, the temperature distribution at numerous points set within the plane of the electrostatic chuck 3 is measured in advance, and the temperatures at the inlet and outlet of the refrigerant gas are also measured at that time. In this way, the correlation between the temperatures at the inlet and outlet of the refrigerant gas and the temperature distribution at multiple examples of the temperature distribution of the electrostatic chuck 3 is experimentally determined in advance and stored as correlation data in a storage device.

[0039] When performing control, the temperature distribution of the electrostatic chuck 3 at that time is predicted by measuring the temperatures of the refrigerant gas inlet and outlet. Then, the necessary temperatures for the refrigerant gas inlet and outlet to achieve the optimal temperature distribution of the electrostatic chuck 3 in this case are detected from the storage device, and the temperatures of the refrigerant gas inlet and outlet are set to those temperatures. In this way, by controlling the temperatures of the refrigerant gas inlet and outlet, an optimal temperature distribution can be achieved for the electrostatic chuck 3.

[0040] Next, we will explain how to correct the temperature distribution of an electrostatic chuck with greater accuracy. In the embodiment described above, a method was explained for making the temperature distribution on the electrostatic chuck 3 uniform using only the refrigerant gas flowing through the piping. This alone can create a uniform temperature distribution on the electrostatic chuck 3, but if there are inconsistencies in the temperature distribution, a heater can be added to enable more precise temperature control.

[0041] Figure 3 shows an example of a temperature compensation device for performing temperature compensation using a heater. In the temperature compensation device 50 shown in Figure 3, ten x-axis control lines 1, 2, 3...10, which extend in the x-axis direction, are arranged at equal intervals in the y-axis direction. Similarly, ten y-axis control lines A, B, C...J, which extend in the y-axis direction, are arranged at equal intervals in the x-axis direction.

[0042] At the intersection of x-axis control line 1 and y-axis control line A, heater 53A1 is connected via diode 51A1. Similarly, at the intersection of x-axis control line 1 and y-axis control line B, heater 53B1 is connected via diode 51B1. At other intersections, heater 53 and diode 51 are connected in the same manner. The temperature compensation device 50 is positioned above the electrostatic chuck 3 and parallel to the electrostatic chuck 3, as shown in Figure 4, for example.

[0043] In this configuration, a preliminary evaluation is first performed, and the temperature distribution at numerous points set within the plane of the electrostatic chuck 3 is measured and saved in advance. These points are, for example, the positions of the electrostatic chuck 3 facing the heater 53 installed in the temperature compensation device 50. Then, when controlling with the temperature compensation device 50, the temperature of the heaters in other parts is raised to match the highest temperature part in the plane of the electrostatic chuck 3. To raise the heater temperature, current is passed between the x-axis control line and the y-axis control line corresponding to the part whose temperature is to be raised.

[0044] Specifically, first, the x-axis control line 1 is specified. Next, the intersection points of the y-axis control lines A, B, C, ... J with the x-axis control line 1 where the temperature needs to be increased are specified. Then, for intersection points with low temperatures, the heater 53 is turned on for, for example, 2 / 10 of a second. On the other hand, for areas with high temperatures, the heater 53 is turned on for, for example, 1 / 10 of a second. In this way, the temperature distribution along the x-axis control line 1 is made uniform. Once control is complete for the x-axis control line 1, control is performed for the next x-axis control line 2. This process is repeated until the last x-axis control line 10 is reached. After one cycle, the process returns to the first x-axis control line 1 and repeats.

[0045] Here, the on-time of the heater 53 may be adjusted while actually measuring the temperature distribution. However, the relationship between the chiller output and the temperature correction value at numerous points set within the plane of the electrostatic chuck 3 is measured experimentally in advance and stored in a memory device. Then, the on-time of the heater 53 for each intersection point is predetermined.

[0046] Then, when performing temperature compensation, the current output of the chiller is read first. The on-time of the current to be supplied to the heater 53 at each intersection point, determined from the chiller output at this point, is read from the memory device, and the heater 53 may be controlled based on this on-time. This allows for temperature correction by the heater 53 in addition to temperature control by the refrigerant gas, enabling even more precise and uniform temperature control of the electrostatic chuck 3.

[0047] Next, we will explain how to perform energy-saving operation. When the chiller's required output is not very high, one chiller is stopped and only one other chiller is operated. This enables energy-saving operation. In this case as well, the relationship between the chiller's output and the temperature correction value at numerous points set within the plane of the electrostatic chuck 3 is measured experimentally in advance and stored in a memory device. The on-time of the heater 53 at each intersection point is then predetermined.

[0048] Then, when performing temperature compensation, the current output of the chiller is read first. The on-time of the current to be supplied to the heater 53 at each intersection point, determined from the chiller output at this point, is read from the memory device, and the heater 53 may be controlled based on this on-time.

[0049] As a result, even when operating with only one chiller, temperature correction can be performed by the heater 53 in addition to temperature control by the refrigerant gas, allowing for highly accurate and uniform temperature control of the electrostatic chuck 3. Furthermore, the present invention can be modified and combined in various ways without departing from the spirit of the invention, and it goes without saying that the present invention also applies to such modifications and combinations. [Explanation of Symbols]

[0050] 1 Chamber 3. Electrostatic Chuck 7 Process gases 10, 20 Temperature control system 11, 33 base 11A Upper part of the base 11B Base lower part 13 Chiller 21, 23, 41 Piping 21a, 23a, 41a Piping inlet 21b, 23b, 41b piping outlet 22, 24 Refrigerant gas 25, 29 Inlet piping 27, 31 Discharge piping 50 Temperature compensation device 51 Diodes 53 Heater

Claims

1. An electrostatic chuck installed inside the chamber, The system includes a first chiller and a second chiller for cooling the electrostatic chuck, The base at the bottom of the electrostatic chuck is formed with a first flow path through which the first temperature-controlled medium from the first chiller flows, and a second flow path through which the second temperature-controlled medium from the second chiller flows. In the first flow path, the first temperature control medium flows in from the outer circumference side of the base and is discharged from the inner circumference side. On the other hand, the temperature control system is characterized in that, in the second flow path, the second temperature control medium flows in from the inner circumference side of the base and is discharged from the outer circumference side, thereby controlling the temperature on the electrostatic chuck.

2. The temperature control system according to claim 1, characterized in that the first channel and the second channel are formed in a spiral shape.

3. The temperature control system according to claim 1, characterized in that the first channel and the second channel are composed of a multi-layer structure of two or more layers.

4. The temperature control system according to claim 1, characterized in that the timing of introducing the first temperature control medium and the second temperature control medium and the flow rate per unit time are the same.

5. The temperature control system according to claim 1, characterized in that either the first chiller or the second chiller is stopped and only the other chiller is operated.

6. The temperature control system according to any one of claims 1 to 5, characterized in that it comprises a heating means capable of heating the base at least partially.

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