Plasma processing apparatus and plasma processing method

Abstract

To provide a plasma processing apparatus capable of improving controllability of a temperature of a semiconductor substrate.SOLUTION: A plasma processing apparatus 10 comprises: a substrate holder 40 that holds a semiconductor substrate W; a gas supply part 70 that supplies a mixture gas to each of gas supply spaces F11 and F12 formed between the semiconductor substrate W and the substrate holder 40; flow amount adjustment parts 71 and 72 each of which adjusts each flow amount of two or more type gases contained in the mixture gas; and a flow amount control part 202 that controls the flow amount adjustment parts 71 and 72. The mixture gas contains a helium gas and an argon gas. The flow amount control part 202 executes a first flow amount control that makes a flow amount of the helium gas more than the flow amount of the argon gas in a plasma atmosphere, and a second flow amount control that makes the flow amount of the argon gas more than the flow amount of the helium gas.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present embodiment relates to a plasma processing apparatus and a plasma processing method. [Background technology]

[0002] A plasma dry etching apparatus is one type of plasma processing apparatus that includes a substrate holder for holding a substrate such as a semiconductor substrate, and controls the temperature of the substrate by supplying helium gas and a coolant between the front surface of the substrate holder and the back surface of the substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-129054 Summary of the Invention [Problem to be solved by the invention]

[0004] According to the present embodiment, a plasma processing apparatus and a plasma processing method are provided that can improve the controllability of the substrate temperature. [Means for solving the problem]

[0005] A plasma processing apparatus according to an embodiment is a plasma processing apparatus that introduces a gas into a chamber and processes a substrate placed in the chamber in a plasma atmosphere, and includes a holder that holds the substrate, a gas supply unit that supplies a mixed gas containing two or more gases with different thermal conductivities to a gas supply space formed between the substrate and the holder, a flow rate adjuster that adjusts the flow rates of the two or more gases contained in the mixed gas, and a flow rate controller that controls the flow rate adjuster. The mixed gas contains a first gas and a second gas. The flow rate controller performs a first flow rate control that makes the flow rate of the first gas greater than the flow rate of the second gas in the plasma atmosphere, and a second flow rate control that makes the flow rate of the second gas greater than the flow rate of the first gas. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a block diagram showing a schematic configuration of a plasma processing apparatus according to a first embodiment. [Figure 2] 4 is a flowchart showing the procedure of processing executed by a control unit of the first embodiment. [Figure 3] FIG. 10 is a block diagram showing a schematic configuration of a plasma processing apparatus according to a second embodiment. [Figure 4] 10 is a timing chart showing the transition of the temperature of a semiconductor substrate in a plasma processing apparatus of a comparative example. [Figure 5] 10 is a timing chart showing the transition of the temperature of a semiconductor substrate in a plasma processing apparatus according to a second embodiment. [Figure 6] FIG. 10 is a block diagram showing a schematic configuration of a plasma processing apparatus according to a third embodiment. [Figure 7] FIG. 11 is a block diagram showing a schematic configuration of a plasma processing apparatus according to a first modified example of the third embodiment. [Figure 8] FIG. 11 is a block diagram showing a schematic configuration of a plasma processing apparatus according to a second modified example of the third embodiment. [Figure 9] 9 is a cross-sectional view showing a cross-sectional structure taken along line IX-IX in FIG. 8. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, an embodiment of a plasma processing apparatus and a plasma processing method will be described with reference to the drawings. To facilitate understanding of the description, the same components in the drawings will be denoted by the same reference numerals as much as possible, and duplicated descriptions will be omitted. First Embodiment 1 is a so-called plasma dry etching apparatus that etches a semiconductor substrate having a film to be processed formed thereon using a method such as RIE (Reactive Ion Etching). The plasma processing apparatus 10 of the present embodiment is not limited to a plasma dry etching apparatus, and may also be a plasma processing apparatus for plasma CVD (Chemical Vapor Deposition) or the like. The plasma processing apparatus 10 includes a chamber 20, a shower head 30, a substrate holder 40, an edge ring 50, a plasma electrode 60, and a gas supply unit 70.

[0008] The chamber 20 is a box-shaped member that forms a space for accommodating the semiconductor substrate W. The interior of the chamber 20 is depressurized and in a vacuum state. The semiconductor substrate W may be, for example, a semiconductor wafer such as a silicon wafer, but is not limited to semiconductors and may be a substrate such as a quartz substrate. The semiconductor substrate W has, for example, a multilayer film including a film to be processed and a circuit pattern formed in the multilayer film.

[0009] The showerhead 30 is provided inside the upper wall of the chamber 20. The showerhead 30 is hollow. The showerhead 30 has a large number of holes that open toward the substrate holder 40, and etching gas is introduced into the internal space of the chamber 20 through these holes. The chamber 20 is provided with an exhaust unit 21. Used etching gas is exhausted to the outside through the exhaust unit 21.

[0010] The substrate holder 40 holds the semiconductor substrate W placed on its surface. The substrate holder 40 is made of an insulating material such as ceramic. A plurality of support portions 41 to 43 are provided on the surface of the substrate holder 40. The support portion 41 is a conical protrusion provided in the central portion of the substrate holder 40. The support portions 42 and 43 are ring-shaped protrusions formed to extend concentrically around the support portion 41. The support portion 43 is provided outside the support portion 42. In this embodiment, the substrate holder 40 corresponds to the holding portion.

[0011] An electrode 44 is provided inside the substrate holder 40. A voltage is applied to the electrode 44 from a power supply 45. The substrate holder 40 is a so-called electrostatic chuck that attracts the semiconductor substrate W by Coulomb force generated between the semiconductor substrate W and the electrode 44 to which the voltage is applied, thereby holding the semiconductor substrate W in close contact with the tip ends of the support portions 41 to 43. Of the gaps formed between the substrate holder 40 and the semiconductor substrate W, the gap formed between the support portion 41 and the support portion 42 forms a first gas supply space F11, and the gap formed between the support portion 42 and the support portion 43 forms a second gas supply space F12. In this embodiment, the first gas supply space F11 and the second gas supply space F12 are connected to each other. Gas is supplied to the gas supply spaces F11 and F12 from a gas supply unit 70.

[0012] The edge ring 50 is provided around the substrate holder 40. The edge ring 50 is an annular member integrally assembled with the substrate holder 40. The edge ring 50 suppresses the semiconductor substrate W from shifting in position. The plasma electrode 60 is provided inside or on the bottom of the substrate holder 40. A high-frequency power supply 90 and a matching circuit 91 are connected to the plasma electrode 60. The high-frequency power supply 90 applies a high-frequency voltage to the plasma electrode 60. The matching circuit 91 is provided between the plasma electrode 60 and the high-frequency power supply 90.

[0013] In this plasma processing apparatus 10, the shower head 30 is electrically grounded. Therefore, a high-frequency voltage is applied between the plasma electrode 60 and the shower head 30. This high-frequency voltage causes the etching gas supplied from the shower head 30 to enter the chamber 20 into a plasma state, and the surface of the semiconductor substrate W is etched in the plasma atmosphere. A matching circuit 91 is provided to match the impedance of the high-frequency power supply 90 with that of the plasma and suppress power reflection.

[0014] A coolant flow path 80 is formed inside the plasma electrode 60. An inlet path 81 is connected to the upstream portion of the coolant flow path 80. An outlet path 82 is connected to the downstream portion of the coolant flow path 80. The inlet path 81 and the outlet path 82 are connected to a coolant circulation device (chiller) (not shown). A coolant cooled in the coolant circulation device flows into the coolant flow path 80 through the inlet path 81. The coolant that has flowed through the coolant flow path 80 flows into the coolant circulation device through the outlet path 82 and is cooled again. During plasma processing, the coolant flowing through the coolant flow path 80 cools the plasma electrode 60, thereby controlling the temperature of the plasma electrode 60. The coolant flowing through the coolant flow path 80 cools the semiconductor substrate W via the plasma electrode 60, the substrate holder 40, and gas in the gas supply spaces F11 and F12, thereby controlling the temperature of the semiconductor substrate W. The coolant may be, for example, a gas such as nitrogen or fluorine, or a liquid such as water or an ionic liquid.

[0015] The gas supply unit 70 supplies gas through a gas supply path 75 to gas supply spaces F11 and F12 formed between the substrate holder 40 and the semiconductor substrate W. The gas supply unit 70 includes flow rate adjusters 71 and 72 and a pressure gauge 73. The upstream portion of gas supply path 75 branches into two paths 751 and 752. Helium (He) gas is supplied to first branch path 751 at a predetermined pressure. A gas having a lower thermal conductivity than helium gas, such as argon (Ar) gas, neon (Ne) gas, or chlorofluorocarbon gas, is supplied to second branch path 752 at a predetermined pressure. The following description will be given taking as an example a case where argon gas is supplied to second branch path 752.

[0016] Helium gas is supplied to the gas supply path 75 from the first branch flow path 751, and argon gas is supplied to the gas supply path 75 from the second branch flow path 752. Therefore, a mixed gas of helium gas and argon gas flows through the gas supply path 75. This mixed gas is supplied through the gas supply path 75 to gas supply spaces F11, F12 formed between the substrate holder 40 and the semiconductor substrate W. Therefore, the mixed gas of helium gas and argon gas is supplied to the bottom surface of the semiconductor substrate W as a backside gas.

[0017] The flow rate adjuster 71 is provided in the first branch flow path 751. The flow rate adjuster 71 adjusts the flow rate of helium gas flowing from the first branch flow path 751 to the gas supply path 75. The flow rate adjuster 72 is provided in the second branch flow path 752. The flow rate adjuster 72 adjusts the flow rate of argon gas flowing from the second branch flow path 752 to the gas supply path 75.

[0018] The pressure gauge 73 is provided in the gas supply path 75. The pressure gauge 73 detects the pressure of the mixed gas flowing through the gas supply path 75, and outputs a signal to the control unit 200 according to the detected pressure of the mixed gas. The plasma processing apparatus 10 includes a control unit 200 for controlling the plasma processing apparatus 10. The control unit 200 controls, for example, flow rate adjustment units 71 and 72. The control unit 200 is mainly configured with a microcomputer having a CPU, a storage device, etc. The control unit 200 includes a pressure acquisition unit 201 and a flow rate control unit 202 as functional components realized by the CPU executing a program stored in the storage device.

[0019] The pressure acquisition unit 201 acquires information on the pressure of the mixed gas flowing through the gas supply path 75, in other words, the pressure of the mixed gas supplied to the gas supply spaces F11, F12 formed between the substrate holder 40 and the semiconductor substrate W, based on the output signal of the pressure gauge 73. The flow rate control unit 202 controls the flow rate adjustment units 71 and 72 to maintain the pressure of the mixed gas at a predetermined pressure and to change the flow rate ratio of helium gas and argon gas contained in the mixed gas.

[0020] Next, a specific procedure of control executed by the flow rate control unit 202 will be described with reference to Fig. 2. The process shown in Fig. 2 is repeatedly executed at predetermined intervals in a plasma atmosphere while a plasma process such as dry etching is being performed on the semiconductor substrate W. As shown in FIG. 2, the flow rate control unit 202 first determines whether or not a situation exists in which low-temperature etching such as cryo-etching is to be performed (step S10).

[0021] For example, in the manufacturing process of NAND flash memory, plasma dry etching is sometimes used to form holes such as memory holes and contact holes in a semiconductor substrate W. In the hole forming process, for example, when forming a hole in a film to be processed on the semiconductor substrate W, it is necessary to process the film to be processed larger (deeper). In such cases, it is desirable for the temperature of the semiconductor substrate W to be lower. On the other hand, in the process of fine-tuning the shape and size of a hole after it has been formed in the semiconductor substrate W, it is necessary to process the semiconductor substrate W to be smaller (shallower). In such cases, it is desirable for the temperature of the semiconductor substrate W to be higher.

[0022] As described above, when processing a film to be processed on a semiconductor substrate W, it is effective to selectively use a low-temperature etching process for etching a semiconductor substrate W at a low temperature, and a high-temperature etching process for etching a semiconductor substrate W at room temperature, depending on the specific nature of the processing. In this embodiment, the timing and duration of each of the low-temperature etching process and the high-temperature etching process are mapped and stored in the storage device of the control unit 200. After starting the etching process, the flow rate control unit 202 determines whether or not the situation is such that the low-temperature etching process should be performed, based on the map stored in the control unit 200.

[0023] When the flow rate control unit 202 determines that the low-temperature etching process is being performed (step S10: YES), it executes the first flow rate control (step S11). Specifically, as the first flow rate control, the flow rate control unit 202 controls the flow rate adjustment units 71 and 72 so that the flow rate of helium gas contained in the mixed gas is greater than the flow rate of argon gas while maintaining the pressure of the mixed gas at a predetermined pressure. For example, the flow rate control unit 202 controls the flow rate adjustment units 71 and 72 so that the flow rates of helium gas and argon gas contained in the mixed gas are "flow rate of helium gas:flow rate of argon gas=10:0." Increasing the flow rate ratio of helium gas contained in the mixed gas in this way increases the thermal conductivity of the mixed gas, making it easier for the heat of the semiconductor substrate W to be absorbed by the coolant via the mixed gas. In other words, the semiconductor substrate W is more easily cooled, and the actual temperature of the semiconductor substrate W can be reduced. For example, when the temperature of the coolant is "-20°C," it is possible to reduce the temperature of the semiconductor substrate W to approximately "0°C." In this embodiment, helium gas corresponds to the first gas, and argon gas corresponds to the second gas.

[0024] On the other hand, if the flow rate control unit 202 makes a negative determination in step S10 (step S10: NO), that is, if it determines that a situation exists in which high-temperature etching processing is to be performed, it executes the second flow rate control (step S12). Specifically, the flow rate control unit 202 controls the flow rate adjustment units 71 and 72 so that the flow rate of helium gas contained in the mixed gas is less than the flow rate of argon gas while maintaining the pressure of the mixed gas at a predetermined pressure. For example, the flow rate control unit 202 controls the flow rate adjustment units 71 and 72 so that the flow rates of helium gas and argon gas contained in the mixed gas are "helium gas flow rate: argon gas flow rate = 1:9." Increasing the flow rate ratio of argon gas contained in the mixed gas in this way reduces the thermal conductivity of the mixed gas, making it more difficult for the heat of the semiconductor substrate W to be absorbed by the coolant via the mixed gas. Therefore, the semiconductor substrate W is more easily cooled, and the actual temperature of the semiconductor substrate W can be increased. For example, when the temperature of the coolant is "-20°C," it is possible to raise the temperature of the semiconductor substrate W to approximately "80°C." As described above, the control performed by the flow rate control unit 202 repeatedly executes the process shown in Fig. 2. Therefore, the flow rate control unit 202 may execute both the first flow rate control and the second flow rate control.

[0025] As described above, the plasma processing apparatus 10 of this embodiment includes the substrate holder 40, the gas supply unit 70, the flow rate adjustment units 71 and 72, and the flow rate control unit 202. The substrate holder 40 holds a semiconductor substrate W. The gas supply unit 70 supplies a mixed gas containing helium gas and argon gas, two types of gas with different thermal conductivities, to the gas supply spaces F11 and F12 formed between the semiconductor substrate W and the substrate holder 40. The flow rate adjustment units 71 and 72 adjust the flow rates of the helium gas and argon gas contained in the mixed gas. The flow rate control unit 202 performs a first flow rate control in which the flow rate of helium gas is made greater than the flow rate of argon gas in the plasma atmosphere, and a second flow rate control in which the flow rate of argon gas is made greater than the flow rate of helium gas. This configuration allows the thermal conductivity of the mixed gas to be changed, thereby improving the temperature controllability of the semiconductor substrate W.

[0026] Note that changing the temperature of the coolant is also a possible method for changing the temperature of the semiconductor substrate W. However, since it takes a considerable amount of time for the temperature of the semiconductor substrate W to actually change after the temperature of the coolant is changed, there is a concern that the temperature responsiveness of the semiconductor substrate W may be slow. In this regard, if the thermal conductivity of the mixed gas is changed as in this embodiment, the temperature of the semiconductor substrate W can be changed more quickly, thereby improving the temperature responsiveness of the semiconductor substrate W.

[0027] Furthermore, as a comparative example, when helium gas alone is used as the backside gas for the semiconductor substrate W, it is also possible to change the temperature of the semiconductor substrate W by changing the pressure of the helium gas. In this regard, when a mixed gas is used as the backside gas for the semiconductor substrate W as in this embodiment, the range of change in the thermal conductivity of the backside gas can be increased. As a result, it is possible to increase the range of change in the temperature of the semiconductor substrate W, which improves the manufacturability of the semiconductor substrate W and enables the semiconductor device to be suitably manufactured.

[0028] Second Embodiment Next, a second embodiment of the plasma processing apparatus 10 and plasma processing method will be described, focusing on differences from the plasma processing apparatus 10 and plasma processing method of the first embodiment.

[0029] 3, in the plasma processing apparatus 10 of this embodiment, an upstream portion of the coolant inlet path 81 branches into two paths 811 and 812. A downstream portion of the coolant outlet path 82 branches into two paths 821 and 822. The first inlet branch path 811 and the second outlet branch path 821 are connected to a first coolant circulation device (not shown). The second inlet branch path 812 and the second outlet branch path 822 are connected to a second coolant circulation device (not shown). The temperature of the coolant supplied from the second coolant circulation device to the second inlet branch path 812 is higher than the temperature of the coolant supplied from the first coolant circulation device to the first inlet branch path 811. Hereinafter, the coolant supplied from the first coolant circulation device to the first inlet branch path 811 will be referred to as a "low-temperature coolant," and the coolant supplied from the second coolant circulation device to the second inlet branch path 812 will be referred to as a "high-temperature coolant." In this embodiment, for example, the temperature of the low-temperature refrigerant is set to "10[° C.]" and the temperature of the high-temperature refrigerant is set to "60[° C.]".

[0030] The branch flow paths 811, 812, 821, and 822 are respectively provided with opening and closing valves 813, 814, 823, and 824. The opening and closing valves 813, 814, 823, and 824 open and close the branch flow paths 811, 812, 821, and 822, respectively. The control unit 200 further includes a refrigerant temperature change unit 203 as a functional configuration realized by the CPU executing a program stored in the storage device. The refrigerant temperature change unit 203 changes the temperature of the refrigerant supplied to the refrigerant flow path 80 by controlling the open / close states of the on-off valves 813, 814, 823, and 824.

[0031] Specifically, when lowering the temperature of the coolant flowing through the coolant flow path 80, the coolant temperature changer 203 opens the on-off valves 813 and 823 and closes the on-off valves 814 and 824. As a result, a low-temperature coolant cooled by the first coolant circulation device is supplied to the coolant flow path 80, causing the low-temperature coolant to flow inside the plasma electrode 60. As a result, the heat of the semiconductor substrate W is more easily absorbed by the coolant, and the temperature of the semiconductor substrate W can be further lowered.

[0032] Furthermore, when increasing the temperature of the coolant flowing through the coolant flow path 80, the coolant temperature changer 203 closes the on-off valves 813 and 823 and opens the on-off valves 814 and 824. This causes a high-temperature coolant cooled by the second coolant circulation device to be supplied to the coolant flow path 80, causing the high-temperature coolant to flow inside the plasma electrode 60. As a result, it becomes difficult for the coolant to absorb heat from the semiconductor substrate W, and the temperature of the semiconductor substrate W can be further increased.

[0033] As described above, the plasma processing apparatus 10 of this embodiment includes the coolant temperature change unit 203 that changes the temperature of the coolant supplied to the substrate holder 40. By combining the configuration for changing the temperature of the coolant with the configuration for adjusting the flow rates of the helium gas and the argon gas contained in the mixed gas, the temperature of the semiconductor substrate W can be changed more flexibly.

[0034] For example, in a comparative example, when helium gas alone is used as the backside gas for the semiconductor substrate W, the temperature of the semiconductor substrate W can be changed by changing the pressure of the helium gas, as shown in Fig. 4. That is, when the pressure of the helium gas is changed while a low-temperature refrigerant at 10°C is flowing through the refrigerant flow path 80, the temperature of the semiconductor substrate W can be changed in a range from 20°C to 50°C, as shown by the solid line in Fig. 4. Furthermore, when the pressure of the helium gas is changed while a high-temperature refrigerant at 60°C is flowing through the refrigerant flow path 80, the temperature of the semiconductor substrate W can be changed in a range from 70°C to 100°C, as shown by the dashed line in Fig. 4.

[0035] On the other hand, when a mixture of helium gas and argon gas is used as the backside gas for the semiconductor substrate W as in this embodiment, the temperature of the semiconductor substrate W can be changed as shown in FIG. 5 by changing the flow rate ratio of the helium gas and the argon gas while maintaining a constant pressure of the mixture gas. That is, when the flow rate ratio of the helium gas and the argon gas is changed while a low-temperature refrigerant at 10°C is flowing through the refrigerant flow path 80, the temperature of the semiconductor substrate W can be changed in the range of 30°C to 140°C, as shown by the solid line in FIG. 5. Furthermore, when the flow rate ratio of the helium gas and the argon gas is changed while a high-temperature refrigerant at 60°C is flowing through the refrigerant flow path 80, the temperature of the semiconductor substrate W can be changed in the range of 80°C to 190°C, as shown by the dashed line in FIG. 5. As a result, by using the plasma processing apparatus of this embodiment, the temperature of the semiconductor substrate W can be changed in the range of 30°C to 190°C.

[0036] In this way, by combining a configuration for changing the temperature of the refrigerant with a configuration for adjusting the flow rates of the helium gas and argon gas contained in the mixed gas, it is possible to change the temperature of the semiconductor substrate W more flexibly. The plasma processing apparatus 10 of this embodiment also includes branch flow paths 811, 812, 821, and 822 as a coolant supply unit that supplies two types of coolants with different temperatures to the substrate holder 40. The plasma processing apparatus 10 also includes on-off valves 813, 814, 823, and 824 as a switching unit that individually switches on and off the supply of the two types of coolants with different temperatures to the substrate holder 40. The coolant temperature changing unit 203 changes the temperature of the coolant supplied to the substrate holder 40 by controlling the on-off valves 813, 814, 823, and 824. This configuration makes it easy to change the temperature of the coolant supplied to the substrate holder 40.

[0037] <Third embodiment> Next, a third embodiment of the plasma processing apparatus 10 and plasma processing method will be described, focusing on differences from the plasma processing apparatus 10 and plasma processing method of the first embodiment.

[0038] When a semiconductor substrate W is subjected to plasma processing using the plasma processing apparatus 10 shown in FIG. 1, a temperature distribution occurs in the semiconductor substrate W such that the temperature at the periphery is higher than the temperature at the center. For example, the temperature at the periphery of the semiconductor substrate W is approximately 20°C to 30°C higher than the temperature at the center. This is because the outer edge of the semiconductor substrate W is not in contact with the backside gas, and therefore the temperature tends to be higher at that portion. If the temperature distribution in the semiconductor substrate W becomes non-uniform in this way, variations in the size and shape of holes, for example, are likely to occur when processing a film to be processed on the semiconductor substrate W by plasma processing. In other words, this is undesirable because it deteriorates the processing accuracy of the semiconductor substrate W.

[0039] Therefore, in the plasma processing apparatus 10 of this embodiment, the peripheral portion of the semiconductor substrate W is cooled more than the central portion thereof, thereby making the temperature distribution of the semiconductor substrate W uniform. 6, in the plasma processing apparatus 10 of this embodiment, a first gas supply space F11 and a second gas supply space F12 are formed as independent spaces. In this embodiment, the support portions 41 to 43 formed on the surface of the semiconductor substrate W correspond to partition portions that separate the gap formed between the semiconductor substrate W and the substrate holder 40 into the independent first gas supply space F11 and second gas supply space F12.

[0040] The plasma processing apparatus 10 includes a first gas supply unit 70A that supplies a mixed gas to the first gas supply space F11 and a second gas supply unit 70B that supplies a mixed gas to the second gas supply space F12. Hereinafter, the mixed gas supplied from the first gas supply unit 70A to the first gas supply space F11 will be referred to as the "first mixed gas," and the mixed gas supplied from the second gas supply unit 70B to the second gas supply space F12 will be referred to as the "second mixed gas."

[0041] The configurations of the first gas supply unit 70A and the second gas supply unit 70B are the same as those of the gas supply unit 70 of the first embodiment shown in Fig. 1, and therefore detailed description thereof will be omitted. In Fig. 6, in order to distinguish between the components of the first gas supply unit 70A and the second gas supply unit 70B, the former components are designated with the suffix "A" and the latter components are designated with the suffix "B."

[0042] The flow rate control unit 202 of the control unit 200 controls the flow rate adjustment units 71A and 72A of the first gas supply unit 70A to maintain the pressure of the first mixed gas supplied to the first gas supply space F11 at a predetermined pressure and to change the flow rate ratio of helium gas and argon gas contained in the first mixed gas. The flow rate control unit 202 also controls the flow rate adjustment units 71B and 72B of the second gas supply unit 70B to maintain the pressure of the second mixed gas supplied to the second gas supply space F12 at a predetermined pressure and to change the flow rate ratio of helium gas and argon gas contained in the second mixed gas.

[0043] For example, when the temperature of the coolant flowing through the coolant flow path 80 is 20°C and the temperature of the semiconductor substrate W is controlled to 80°C, the flow rate control unit 202 controls the flow rate adjustment units 71A and 72A of the first gas supply unit 70A so that the flow rate of helium gas contained in the first mixed gas is less than the flow rate of argon gas. For example, the flow rate control unit 202 controls the flow rate adjustment units 71A and 72A so that the flow rates of helium gas and argon gas contained in the mixed gas are "flow rate of helium gas:flow rate of argon gas=2.5:7.5". In this embodiment, the flow rate adjustment units 71A and 72A correspond to first flow rate adjustment units that adjust the flow rates of the two types of gases contained in the first mixed gas.

[0044] Furthermore, the flow rate control unit 202 controls the flow rate adjustment units 71B and 72B of the second gas supply unit 70B so that the flow rate of helium gas contained in the second mixed gas is greater than the flow rate of argon gas. For example, when a temperature difference of about 20°C occurs between the central portion and the peripheral portion of the semiconductor substrate W, the flow rate control unit 202 controls the flow rate adjustment units 71B and 72B so that the flow rates of helium gas and argon gas contained in the second mixed gas become "flow rate of helium gas:flow rate of argon gas=6:4." In this embodiment, the flow rate adjustment units 71B and 72B correspond to second flow rate adjustment units that adjust the flow rates of the two types of gases contained in the second mixed gas.

[0045] The control amounts of the flow rate adjustment units 71A, 72A, 71B, and 72B are determined in advance by experiments or the like, and the control amounts of the flow rate adjustment units 71A, 72A, 71B, and 72B based on the experimental results are stored in a storage device of the control unit 200. The flow rate control unit 202 controls the flow rate adjustment units 71A, 72A, 71B, and 72B based on the control amounts stored in the storage device.

[0046] By controlling the flow rate ratio of helium gas and argon gas in each of the first mixed gas and the second mixed gas in this manner, the thermal conductivity of the backside gas in the peripheral portion of the semiconductor substrate W can be made higher than the thermal conductivity of the backside gas in the central portion of the semiconductor substrate W. In other words, since the peripheral portion of the semiconductor substrate W can be cooled more than the central portion of the semiconductor substrate W, the temperature distribution of the semiconductor substrate W can be made uniform.

[0047] When a temperature difference of about 30°C occurs between the central portion and the peripheral portion of the semiconductor substrate W, the flow control unit 202 controls the flow rate adjustment units 71B, 72B so that the flow rates of the helium gas and argon gas contained in the second mixed gas become "helium gas flow rate: argon gas flow rate = 8:2." In other words, the flow rate of the helium gas contained in the second mixed gas increases as the temperature difference between the central portion and the peripheral portion of the semiconductor substrate W increases. This increases the thermal conductivity of the backside gas in the peripheral portion of the semiconductor substrate W, further cooling the peripheral portion of the semiconductor substrate W, thereby making it possible to uniform the temperature distribution of the semiconductor substrate W.

[0048] As described above, the plasma processing apparatus 10 of this embodiment includes the first gas supply unit 70A that supplies the first mixed gas to the central portion of the semiconductor substrate W, and the second gas supply unit 70B that supplies the second mixed gas to the portion of the semiconductor substrate W that is outer than the central portion. The second mixed gas contains more helium gas, which has a higher thermal conductivity, than the first mixed gas. With this configuration, the second mixed gas, which has a higher thermal conductivity, is supplied to the outer portion of the semiconductor substrate W, which is prone to becoming hot, thereby making it possible to uniformize the temperature of the semiconductor substrate W.

[0049] Flow rate control unit 202 controls first flow rate adjustment units 71A, 72A and second flow rate adjustment units 71B, 72B so that the pressures of the first mixed gas and the second mixed gas become the same predetermined pressure. By controlling the pressures of the first mixed gas and the second mixed gas to the same predetermined pressure as in this configuration, the parameter that affects the temperature of semiconductor substrate W is the flow rate ratio of helium gas and argon gas contained in the mixed gas, making it easier to control the temperature of semiconductor substrate W.

[0050] (First Modification) 7, the plasma processing apparatus 10 of this modification further includes substrate temperature sensors 101 to 103. The substrate temperature sensor 101 has a probe 101a that contacts the central portion of the semiconductor substrate W and directly detects the temperature of the central portion of the semiconductor substrate W via the probe 101a. The substrate temperature sensors 102 and 103 have probes 102a and 103a that contact the outer periphery of the semiconductor substrate W, respectively, and directly detect the temperature of the outer periphery of the semiconductor substrate W via the probes 102a and 103a. The substrate temperature sensors 101 to 103 output signals corresponding to the detected temperatures to the control unit 200.

[0051] The control unit 200 further includes a substrate temperature acquisition unit 204 as a functional configuration realized by the CPU executing a program stored in the storage device. The substrate temperature acquisition unit 204 acquires the temperature Ta of the central portion and the temperature Tb of the peripheral portion of the semiconductor substrate W based on the output signals of the substrate temperature sensors 101 to 103.

[0052] The flow rate control unit 202 controls the flow rate adjustment units 71A, 72A, 71B, and 72B of each gas supply unit 70A, 70B based on the temperature Ta of the central portion and the temperature Tb of the peripheral portion of the semiconductor substrate W acquired by the substrate temperature acquisition unit 204. For example, the flow rate control unit 202 calculates the deviation between the temperature Ta of the central portion of the semiconductor substrate W and a predetermined target temperature T*, and controls the flow rate adjustment units 71A and 72A of the first gas supply unit 70A so that the flow rate of helium gas contained in the first mixed gas increases and the flow rate of argon gas decreases as the calculated temperature deviation ΔTa (=Ta−T*) increases. In addition, the flow rate control unit 202 calculates the deviation between the temperature Tb of the outer peripheral portion of the semiconductor substrate W and a predetermined target temperature T*, and controls the flow rate adjustment units 71B, 72B of the second gas supply unit 70B so that the flow rate of helium gas contained in the second mixed gas increases and the flow rate of argon gas decreases as the calculated temperature deviation ΔTb (=Tb-T*) increases.

[0053] In this manner, the flow rate control unit 202 of this modification controls the first flow rate adjustment units 71A, 72A and the second flow rate adjustment units 71B, 72B based on the temperatures Ta, Tb of the semiconductor substrate W. According to this configuration, the two types of gases contained in the first mixed gas and the second mixed gas are adjusted based on the temperatures Ta, Tb of the semiconductor substrate W. That is, since the thermal conductivity of each of the first mixed gas and the second mixed gas is adjusted, it becomes easier to make the temperature of the semiconductor substrate W more uniform.

[0054] (Second Modification) The plasma processing apparatus 10 of this modification estimates the temperature of the semiconductor substrate W based on the temperature of the coolant, and then controls the flow rate adjusters 71A, 72A, 71B, and 72B based on the estimated temperature of the semiconductor substrate W.

[0055] Specifically, as shown in FIG. 8, coolant flow paths 83 and 84 that are independent of each other are formed inside substrate holder 40. FIG. 9 shows a cross-sectional structure of substrate holder 40 taken along line IX-IX in FIG. 8. As shown in FIG. 9, first coolant flow path 83 is formed in the central portion of substrate holder 40 so as to extend in a double circular shape. Second coolant flow path 84 is formed in the outer periphery of substrate holder 40 so as to extend in a double circular shape. As shown in FIG. 8, first coolant flow path 83 is disposed at a position corresponding to first gas supply space F11. Second coolant flow path 84 is disposed at a position corresponding to second gas supply space F12. Hereinafter, the coolant flowing through first coolant flow path 83 will also be referred to as the "first coolant," and the coolant flowing through second coolant flow path 84 will also be referred to as the "second coolant."

[0056] 9, the upstream portions of the first refrigerant flow path 83 and the second refrigerant flow path 84 are connected to a common inflow path 81. Therefore, refrigerant at the same temperature flows into the first refrigerant flow path 83 and the second refrigerant flow path 84 from the inflow path 81. The inflow path 81 is provided with a temperature sensor 110 that detects a temperature T0 of the refrigerant flowing through the inflow path 81. The temperature sensor 110 detects the refrigerant temperature T0 and outputs a signal corresponding to the detected refrigerant temperature T0 to the control unit 200.

[0057] The downstream portions of the first refrigerant flow path 83 and the second refrigerant flow path 84 are connected to branch flow paths 861 and 862, respectively. The downstream portions of the branch flow paths 861 and 862 are connected to a common outflow path 86. Therefore, the refrigerant that flows through the first refrigerant flow path 83 and the second refrigerant flow path 84 flows to the outflow path 86 via the branch flow paths 861 and 862. The branch flow paths 861 and 862 are provided with temperature sensors 121 and 122 and flow velocity sensors 131 and 132, respectively. The temperature sensors 121 and 122 detect temperatures T1 and T2 of the refrigerant flowing through the branch flow paths 861 and 862, respectively, and output signals corresponding to the detected refrigerant temperatures T1 and T2 to the control unit 200. The flow velocity sensors 131 and 132 detect flow velocities V1 and V2 of the refrigerant flowing through the branch flow paths 861 and 862, respectively, and output signals corresponding to the detected refrigerant flow velocities V1 and V2 to the control unit 200, respectively.

[0058] The control unit 200 further includes a refrigerant temperature acquisition unit 205 as a functional component realized by the CPU executing a program stored in the storage device. The refrigerant temperature acquisition unit 205 acquires a pre-passage temperature T0, which is the temperature of the refrigerant before passing through the first refrigerant flow path 83 and the second refrigerant flow path 84, based on the output signal of the temperature sensor 110. The refrigerant temperature acquisition unit 205 also acquires a first post-passage temperature T1, which is the temperature of the refrigerant after passing through the first refrigerant flow path 83, and a second post-passage temperature T2, which is the temperature of the refrigerant after passing through the second refrigerant flow path 84, based on the output signals of the temperature sensors 121 and 122, respectively.

[0059] The flow control unit 202 of the control unit 200 controls the flow adjustment units 71A, 72A, 71B, and 72B based on the pre-pass temperature T0, the first post-pass temperature T1, and the second post-pass temperature T2 acquired by the refrigerant temperature acquisition unit 205, and the refrigerant flow velocities V1 and V2 detected by the flow velocity sensors 131 and 132.

[0060] For example, the flow rate control unit 202 calculates a first temperature change ΔT1, which is the amount of temperature change per unit time of the first refrigerant flowing through the first refrigerant flow path 83, based on the following equation f1 using the pre-passage temperature T0 and the first post-passage temperature T1 acquired by the refrigerant temperature acquisition unit 205 and the refrigerant flow velocity V1 detected by the flow velocity sensor 131. In the following equation f1, "L1" is the flow path length of the first refrigerant flow path 83.

[0061] ΔT1=(T1-T0)×V1 / L1 (f1) Furthermore, the flow rate control unit 202 calculates a second temperature change amount ΔT2, which is the amount of temperature change per unit time of the second refrigerant flowing through the second refrigerant flow path 84, based on the following formula f2. In the following formula f2, "L2" is the flow path length of the second refrigerant flow path 84.

[0062] ΔT2=(T2-T0)×V2 / L2 (f2) The first refrigerant flowing through the first refrigerant flow path 83 absorbs heat from the central portion of the semiconductor substrate W via the first mixed gas supplied to the first gas supply space F11. Therefore, the first temperature change amount ΔT1 calculated by the above formula f1 is correlated with the temperature of the central portion of the semiconductor substrate W. Similarly, the second temperature change amount ΔT2 calculated by the above formula f2 is correlated with the temperature of the peripheral portion of the semiconductor substrate W.

[0063] Using this, the flow rate control unit 202 of the control unit 200 controls the flow rate adjustment units 71A and 72A of the first gas supply unit 70A so that the first temperature change amount ΔT1 becomes a predetermined value. Similarly, the flow rate control unit 202 controls the flow rate adjustment units 71B and 72B of the second gas supply unit 70B so that the second temperature change amount ΔT2 becomes a predetermined value.

[0064] According to the plasma processing apparatus 10 of this modification, the first temperature change amount ΔT1 and the second temperature change amount ΔT2 are controlled to the same predetermined value, which results in the temperature of the central portion and the temperature of the peripheral portion of the semiconductor substrate W being more easily matched. Therefore, the temperature of the semiconductor substrate W is more easily made uniform.

[0065] The flow rate control unit 202 may control the flow rate adjustment units 71A and 72A of the first gas supply unit 70A and the flow rate adjustment units 71B and 72B of the second gas supply unit 70B so that the first temperature change amount ΔT1 and the second temperature change amount ΔT2 are in a predetermined ratio. Even with such a configuration, it is possible to obtain the same or similar actions and effects.

[0066] <Other embodiments> The present disclosure is not limited to the specifics set forth above. For example, the mixed gas supplied to the substrate holder 40 and the semiconductor substrate W is not limited to a mixed gas containing two types of gas, helium gas and argon gas, but may be a mixed gas containing three or more types of gases with different thermal conductivities.

[0067] In the plasma processing apparatus 10 of each embodiment, the pressure of the mixed gas may be changed. For example, in the plasma processing apparatus 10 of the second embodiment, the pressure of the first mixed gas may be different from the pressure of the second mixed gas. <Example of manufacturing method of semiconductor device> An example of a method for manufacturing a semiconductor device using the plasma processing methods according to the first to third embodiments will be described below. The semiconductor device is a three-dimensional NAND flash memory.

[0068] In the manufacture of a semiconductor device, for example, the plasma processing methods of the first to third embodiments can be used in a step of forming a memory hole in a laminated body as a film to be processed. The laminated body in the memory hole forming step is, for example, a laminated body in which insulating layers containing silicon oxide and sacrificial layers containing silicon nitride are alternately stacked, and the semiconductor device is manufactured through a step of filling the formed memory hole with a memory film and a semiconductor channel.

[0069] The plasma processing methods of the first to third embodiments enable the temperature of a semiconductor substrate to be suitably controlled. For example, when forming a memory hole with a high aspect ratio in a stacked body, low-temperature etching is desirable in order to process the stacked body at high speed. However, high-speed low-temperature etching may result in a partial failure to obtain the desired shape, such as reducing the dimensions of the bottom of the memory hole. In such cases, high-temperature (room-temperature) etching can be performed to adjust the dimensions of the bottom of the memory hole, for example. Furthermore, by switching between low-temperature etching and room-temperature etching at the desired timing, the circularity of the memory hole can be improved. This makes it possible to manufacture high-quality semiconductor devices.

[0070] The present disclosure is not limited to the specifics described above. Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments may be embodied in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments and their modifications are within the scope and spirit of the invention, and are included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0071] F11, F12: gas supply space, W: semiconductor substrate, 10: plasma processing apparatus, 20: chamber, 40: substrate holder (holding portion), 41-43: support portion (partition portion), 70: gas supply portion, 70A: first gas supply portion, 70B: second gas supply portion, 71, 72: flow rate adjustment portions, 71A, 72A: first flow rate adjustment portion, 71B, 72B: second flow rate adjustment portion, 83: first refrigerant flow path, 84: second refrigerant flow path, 202: flow rate control portion, 204: substrate temperature acquisition portion, 205: refrigerant temperature acquisition portion, 811, 812, 821, 822: branch flow path (refrigerant supply portion), 813, 814, 823, 824: opening and closing valves (switching portion).

Claims

1. 1. A plasma processing apparatus that introduces a gas into a chamber and processes a substrate placed in the chamber in a plasma atmosphere, comprising: a holder for holding the substrate; a partitioning section that partitions a gap formed between the substrate and the holder into a plurality of independent gas supply spaces; a plurality of gas supply units that supply gas to the plurality of gas supply spaces, respectively; The plurality of gas supply units include: a first gas supply unit that supplies a first mixed gas, which is a mixture of two or more types of gases having different thermal conductivities, to a central portion of the substrate; a second gas supply unit that supplies a second mixed gas, which is a mixture of two or more types of gases having different thermal conductivities, to a portion of the substrate outer than the central portion, the second mixed gas contains a larger amount of gas having a higher thermal conductivity than the first mixed gas; a refrigerant temperature acquisition unit that acquires the temperature of the refrigerant that cools the holding unit; a first flow rate adjusting unit that adjusts the flow rates of the two or more types of gases contained in the first mixed gas; a second flow rate adjusting unit that adjusts the flow rates of the two or more types of gases contained in the second mixed gas; a flow rate control unit that controls the first flow rate adjustment unit and the second flow rate adjustment unit based on a temperature of the refrigerant, The holding portion has: a first refrigerant flow path through which a first refrigerant flows, the first refrigerant flow path being provided inside the holding unit so as to correspond to a portion through which the first mixed gas flows in the gap between the substrate and the holding unit; a second refrigerant flow path through which a second refrigerant flows, the second refrigerant flow path being provided inside the holding unit so as to correspond to a portion through which the second mixed gas flows in the gap between the substrate and the holding unit; The refrigerant temperature acquisition unit a pre-passage temperature, which is the temperature of the refrigerant before passing through the first refrigerant flow path and the second refrigerant flow path; a first post-passage temperature, which is the temperature of the refrigerant after passing through the first refrigerant flow path; a second post-passage temperature, which is the temperature of the refrigerant after passing through the second refrigerant flow path; and The flow rate control unit calculating a first temperature change amount, which is a temperature change amount of the first refrigerant per unit time, based on a deviation between the pre-passage temperature and the first post-passage temperature; calculating a second temperature change amount, which is a temperature change amount of the second refrigerant per unit time, based on a deviation between the pre-passage temperature and the second post-passage temperature; The first flow rate adjusting unit and the second flow rate adjusting unit are controlled so that the first temperature change amount and the second temperature change amount become predetermined values, or so that the first temperature change amount and the second temperature change amount become a predetermined ratio. Plasma processing equipment.

2. A plasma processing apparatus that introduces a gas into a chamber and processes a substrate placed in the chamber in a plasma atmosphere, comprising: a holder for holding the substrate; a partitioning section that partitions a gap formed between the substrate and the holder into a plurality of independent gas supply spaces; a plurality of gas supply units that supply gas to the plurality of gas supply spaces, respectively; The plurality of gas supply units include: a first gas supply unit that supplies a first mixed gas, which is a mixture of two or more types of gases having different thermal conductivities, to a central portion of the substrate; a second gas supply unit that supplies a second mixed gas, which is a mixture of two or more types of gases having different thermal conductivities, to a portion of the substrate outer than the central portion, the second mixed gas contains a larger amount of gas having a higher thermal conductivity than the first mixed gas; a refrigerant temperature acquisition unit that acquires the temperature of the refrigerant that cools the holding unit; a first flow rate adjusting unit that adjusts the flow rates of the two or more types of gases contained in the first mixed gas; a second flow rate adjusting unit that adjusts the flow rates of the two or more types of gases contained in the second mixed gas; a flow rate control unit that controls the first flow rate adjustment unit and the second flow rate adjustment unit based on a temperature of the refrigerant, The flow rate control unit controls the first flow rate adjustment unit and the second flow rate adjustment unit so that the pressures of the first mixed gas and the second mixed gas are the same predetermined value. Plasma processing equipment.

3. 1. A plasma processing method for introducing an etching gas into a chamber and etching a semiconductor substrate placed in the chamber in a plasma atmosphere, comprising: The semiconductor substrate is held by a holding portion, supplying gases from a plurality of gas supply units to a plurality of independent gas supply spaces formed between the semiconductor substrate and the holding unit, respectively; At least one of the plurality of gas supply units supplies a mixed gas containing two or more types of gases having different thermal conductivities to the gas supply space, The plurality of gas supply units include: a first gas supply unit that supplies a first mixed gas, which is a mixture of two or more types of gases having different thermal conductivities, to a central portion of the semiconductor substrate; a second gas supply unit that supplies a second mixed gas, which is a mixture of two or more types of gases having different thermal conductivities, to a portion of the semiconductor substrate outside the central portion, the second mixed gas contains a larger amount of gas having a higher thermal conductivity than the first mixed gas; acquiring the temperature of the refrigerant that cools the holding unit; adjusting the flow rates of the two or more types of gases contained in the first mixed gas by a first flow rate adjusting unit; adjusting the flow rates of the two or more types of gases contained in the second mixed gas by a second flow rate adjusting unit; The holding portion has: a first refrigerant flow path through which a first refrigerant flows, the first refrigerant flow path being provided inside the holding part so as to correspond to a portion through which the first mixed gas flows in the gap between the semiconductor substrate and the holding part; a second refrigerant flow path through which a second refrigerant flows, the second refrigerant flow path being provided inside the holding part so as to correspond to a portion through which the second mixed gas flows in the gap between the semiconductor substrate and the holding part; a pre-passage temperature, which is the temperature of the refrigerant before passing through the first refrigerant flow path and the second refrigerant flow path, is acquired; a first post-passage temperature, which is the temperature of the refrigerant after passing through the first refrigerant flow path; a second post-passage temperature, which is the temperature of the refrigerant after passing through the second refrigerant flow path; calculating a first temperature change amount, which is a temperature change amount of the first refrigerant per unit time, based on a deviation between the pre-passage temperature and the first post-passage temperature; calculating a second temperature change amount, which is a temperature change amount of the second refrigerant per unit time, based on a deviation between the pre-passage temperature and the second post-passage temperature; The first flow rate adjusting unit and the second flow rate adjusting unit are controlled so that the first temperature change amount and the second temperature change amount become predetermined values, or so that the first temperature change amount and the second temperature change amount become a predetermined ratio. Plasma treatment method.

4. A plasma processing method for introducing an etching gas into a chamber and etching a semiconductor substrate placed in the chamber in a plasma atmosphere, comprising: The semiconductor substrate is held by a holding portion, supplying gases from a plurality of gas supply units to a plurality of independent gas supply spaces formed between the semiconductor substrate and the holding unit, respectively; At least one of the plurality of gas supply units supplies a mixed gas containing two or more types of gases having different thermal conductivities to the gas supply space, The plurality of gas supply units include: a first gas supply unit that supplies a first mixed gas, which is a mixture of two or more types of gases having different thermal conductivities, to a central portion of the semiconductor substrate; a second gas supply unit that supplies a second mixed gas, which is a mixture of two or more types of gases having different thermal conductivities, to a portion of the semiconductor substrate outside the central portion, the second mixed gas contains a larger amount of gas having a higher thermal conductivity than the first mixed gas; acquiring the temperature of the refrigerant that cools the holding unit; adjusting the flow rates of the two or more types of gases contained in the first mixed gas by a first flow rate adjusting unit; adjusting the flow rates of the two or more types of gases contained in the second mixed gas by a second flow rate adjusting unit; The first flow rate adjusting unit and the second flow rate adjusting unit are controlled so that the pressures of the first mixed gas and the second mixed gas are the same predetermined value. Plasma treatment method.

Images