Gas supply system, gas supply method, and program for gas supply system for electrostatic chuck device

Abstract

This gas supply system for an electrostatic chuck device supplies thermally conductive gas to a space between a chucking surface of an electrostatic chuck device for chucking an object with electrostatic force and a chucked surface of the object, the system comprising: a plurality of gas supply lines for supplying the thermally conductive gas to each of a plurality of regions set within the space; a common line that is connected to the gas supply lines and introduces the thermally conductive gas to the gas supply lines; and a flow rate calculation unit for calculating the flow rate of the thermally conductive gas being introduced to the gas supply lines from the common line. The flow rate calculation unit calculates the flow rate of the thermally conductive gas being introduced to the gas supply lines on the basis of a flow rate property of a first flow rate resistance element provided to each of the gas supply lines, a primary-side pressure of the first flow rate resistance element, and a secondary-side pressure of the first flow rate resistance element. A pressure sensor for measuring the primary-side pressure is provided to the common line.

Description

Technical Field

[0001] The present invention relates to a gas supply system, a gas supply method, and a program for a gas supply system for an electrostatic chuck device that adsorbs an object by electrostatic force.

Background Art

[0002] Conventionally, in semiconductor manufacturing processes using plasma processing devices such as plasma etching devices and plasma CVD devices, an electrostatic chuck device has been used to fix a sample such as a silicon wafer in a vacuum chamber. This electrostatic chuck device includes an adsorption plate that adsorbs an object by electrostatic force and a metal base plate that contacts the back surface of the adsorption plate. By using the electrostatic chuck device to adsorb the back surface (adsorbed surface) of the silicon wafer with the adsorption plate, the silicon wafer can be fixed, and for example, the plasma heat applied to the silicon wafer can be released to the base plate side for cooling, achieving uniformization of the surface temperature distribution.

[0003] By the way, fine irregularities exist on the adsorption surface of the adsorption plate and the adsorbed surface of the silicon wafer. Therefore, even when the silicon wafer is adsorbed by the electrostatic chuck device, a minute space with a thickness of about 10 μm is generated between the adsorbed surface and the adsorption surface, and the physical contact area becomes small, resulting in a decrease in the efficiency of heat conduction. Conventionally, a plurality of gas supply ports are provided on the adsorption surface of the adsorption plate, and a heat conductive gas is supplied to the space between the adsorbed surface of the silicon wafer and the adsorption surface of the adsorption plate, so as to efficiently release the plasma heat applied to the silicon wafer to the adsorption plate side (Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the semiconductor manufacturing process using the plasma processing apparatus described above, it is necessary to improve the uniformity of the surface temperature of the object, such as a wafer. This uniformity of the wafer surface temperature depends on the pressure of the thermal conductive gas in multiple regions between the adsorption surface and the adsorbed surface (also called the wafer back surface pressure), and the wafer back surface pressure in each of these regions depends on the flow rate of the thermal conductive gas supplied from the gas supply port corresponding to each region. Therefore, in order to improve the uniformity of the wafer surface temperature distribution, it is important to understand the flow rate of the thermal conductive gas supplied to each region. On the other hand, understanding the flow rate of the thermal conductive gas supplied to each region increases the number of parts, which leads to an increase in manufacturing costs.

[0006] This invention was made to solve the above problems all at once, and its main objective is to improve the uniformity of the surface temperature distribution of objects such as wafers in a gas supply system for electrostatic chuck devices, while also reducing the number of parts and thereby reducing manufacturing costs. [Means for solving the problem]

[0007] In other words, the gas supply system for an electrostatic chuck device according to the present invention supplies a thermally conductive gas to the space between the adsorption surface of an electrostatic chuck device that adsorbs an object by electrostatic force and the adsorbed surface of the object, and comprises a plurality of gas supply lines that supply the thermally conductive gas to each of a plurality of regions set in the space, a common line connected to each of the gas supply lines and introducing the thermally conductive gas into each of the gas supply lines, and a flow rate calculation unit that calculates the flow rate of the thermally conductive gas introduced from the common line to each of the gas supply lines, wherein the flow rate calculation unit calculates the flow rate of the thermally conductive gas introduced into each of the gas supply lines based on the flow rate characteristics of a first flow resistance element provided in each of the gas supply lines, the primary side pressure of the first flow resistance element and the secondary side pressure of the first flow resistance element, and a pressure sensor for measuring the primary side pressure is provided in the common line.

[0008] With such a system, it is possible to determine the flow rate of thermally conductive gas flowing through the gas supply lines corresponding to each of the multiple regions set in the space between the adsorption surface and the surface to be adsorbed. By controlling this flow rate, the back surface pressure of the wafer in each region can be controlled, thereby improving the uniformity of the surface temperature distribution of the object, such as a wafer. Here, instead of individually installing a pressure sensor in each gas supply line to measure the primary pressure of the first flow resistance element, which is necessary for calculating the flow rate of the thermally conductive gas flowing through each gas supply line, the pressure sensor is installed in a common line and standardized, thereby reducing the number of parts and lowering manufacturing costs.

[0009] The "first flow resistance element" can be any element that has a flow characteristic in which the flow rate of the thermally conductive gas passing through is determined by the primary pressure and the secondary pressure, and a laminar flow element resistor is particularly preferred.

[0010] A specific embodiment of a gas supply system for individually controlling the flow rate of thermally conductive gas flowing through each gas supply line is one in which a fluid control valve is provided downstream of the first resistive element in each gas supply line, and the opening degree of the fluid control valve is feedback controlled based on the flow rate calculated by the flow rate calculation unit.

[0011] Preferably, a second flow resistance element is provided downstream of the fluid control valve in each of the gas supply lines, and a pressure calculation unit is further provided to calculate the pressure of the thermal conductive gas in each region, wherein the pressure calculation unit calculates the pressure of the thermal conductive gas in each region based on the primary side pressure of the second flow resistance element, the flow rate of the thermal conductive gas passing through the second flow resistance element, and the flow characteristics of the second flow resistance element. In this way, by utilizing the flow characteristics of the flow resistance element, that is, the inherent characteristics that show the relationship between the primary side pressure (e.g., pressure in the gas supply line) and secondary side pressure (e.g., wafer back surface pressure) of the flow resistance element and the flow rate of the thermally conductive gas passing through it, the wafer back surface pressure in each region can be calculated and determined.

[0012] The "second flow resistance element" can be any element that has a flow characteristic in which the flow rate of the thermally conductive gas passing through is determined by the primary and secondary pressures, and a laminar flow resistor is particularly preferred. Laminar flow resistors have excellent processing accuracy and excellent reproducibility, so by using a laminar flow resistor as a flow resistance element, the pressure of the thermally conductive gas in the space between the adsorption surface and the adsorbed surface can be calculated with greater accuracy. In addition, since laminar flow resistors have a high degree of design freedom, the degree of freedom for the outer diameter of the thermally conductive gas outlet can be increased, and the occurrence of arc discharge can be expected to be suppressed.

[0013] Preferably, each of the gas supply lines is provided with a gas supply channel that opens onto the adsorption surface, and in each of the gas supply lines, the second flow resistance element is provided within the gas supply channel. In this way, a flow resistance element is provided in the gas supply channel that opens to the adsorption surface of the adsorption plate, allowing for more accurate calculation of the wafer back surface pressure in each region and further improving the uniformity of the surface temperature distribution of the object, such as a wafer.

[0014] One specific embodiment of the pressure calculation unit is one which calculates the flow rate of the thermal conductive gas passing through the second flow resistance element based on the flow rate calculated by the flow rate calculation unit and a relational expression showing the mass balance of the flow rate of the thermal conductive gas in the gas supply line.

[0015] In order to diagnose the presence or absence of abnormalities on the back surface of the wafer during plasma processing, such as a decrease in the adsorption force to the wafer due to the aging of the equipment or localized warping of the wafer, it is preferable that the gas supply system further includes a diagnostic unit that compares the calculated pressure of the thermal conductive gas with a predetermined reference pressure to diagnose abnormalities in the pressure value of the thermal conductive gas in each region.

[0016] Preferably, the gas supply system is configured to adjust the flow rate of the thermal conductive gas introduced into each gas supply line so that the pressure of the thermal conductive gas calculated by the pressure calculation unit falls within a predetermined range.

[0017] Preferably, the gas supply system is configured such that the plurality of regions are set up by radially dividing the space. With this type of system, the occurrence of localized warping along the circumferential direction of the wafer can be detected by monitoring the pressure and mass flow rate of the thermally conductive gas supplied from each gas supply line.

[0018] In the gas supply system described above, a specific configuration for detecting the occurrence of warping along the circumferential direction of the wafer is such that the diagnostic unit is configured to diagnose the presence or absence of warping of the object based on the mass flow rate of the thermal conductive gas supplied to each of the radially divided regions, or the pressure of the thermal conductive gas in each of the radially divided regions.

[0019] Furthermore, it is preferable that the gas supply system is configured such that the plurality of regions divide the space concentrically, and then further divide the annular region radially. With this type of system, the back surface pressure of the wafer can be controlled by controlling the flow rate of the thermally conductive gas flowing through the gas supply line corresponding to the inner region, thereby improving the uniformity of the surface temperature distribution of the wafer or other object. Furthermore, by monitoring the pressure of the thermally conductive gas supplied from each gas supply line corresponding to each region further divided from the annular region formed on the outside, it is possible to detect the occurrence of localized warping along the circumferential direction of the wafer.

[0020] Another specific embodiment of the gas supply system is one in which the thermally conductive gas is helium gas.

[0021] The system further comprises a second gas introduction line connected upstream of the first flow resistance element in each of the gas supply lines, for introducing a second gas different from the thermal conductive gas into each of the gas supply lines, wherein the flow rate calculation unit calculates the flow rate of the second gas introduced into each of the gas supply lines based on the flow rate characteristics of the first flow resistance element, the primary side pressure of the first flow resistance element, and the secondary side pressure of the first flow resistance element, and preferably a pressure sensor for measuring the primary side pressure is provided in the second gas introduction line. In this way, a separate second gas introduction line for introducing a second gas, such as argon or nitrogen, is provided for each gas supply line, in addition to the common line. This allows for quick switching between the supply of thermal conductive gas and the supply of the second gas. Furthermore, the pressure sensor for measuring the primary side pressure of the flow resistance element, which is necessary for calculating the flow rate of the second gas flowing through each gas supply line, is provided in the second gas introduction line and standardized, thus reducing the number of parts and lowering manufacturing costs.

[0022] Furthermore, the present invention relates to a gas supply method for supplying a thermally conductive gas to the space between the adsorption surface of an electrostatic chuck device that adsorbs an object by electrostatic force and the adsorbed surface of the object, wherein the electrostatic chuck device comprises a plurality of gas supply lines that supply the thermally conductive gas to each of a plurality of regions set in the space, and a common line connected to each of the gas supply lines and introducing the thermally conductive gas into each of the gas supply lines, wherein the flow rate of the thermally conductive gas introduced from the common line to each of the gas supply lines is calculated based on the flow rate characteristics of a first flow resistance element provided in each of the gas supply lines, the primary side pressure of the first flow resistance element, and the secondary side pressure of the first flow resistance element, and the measured value of a pressure sensor provided in the common line is used as the primary side pressure.

[0023] Furthermore, the present invention relates to a program for a gas supply system that supplies a thermally conductive gas to the space between the adsorption surface of an electrostatic chuck device that adsorbs an object by electrostatic force and the adsorbed surface of the object, wherein the electrostatic chuck device comprises a plurality of gas supply lines that supply the thermally conductive gas to each of a plurality of regions set in the space, and a common line connected to each of the gas supply lines that introduces the thermally conductive gas into each of the gas supply lines, and the program causes a computer to perform a flow rate calculation function that calculates the flow rate of the thermally conductive gas introduced from the common line to each of the gas supply lines based on the flow rate characteristics of a first flow resistance element provided in each of the gas supply lines, the primary side pressure of the first flow resistance element, and the secondary side pressure of the first flow resistance element, wherein the flow rate calculation function uses the measured value of a pressure sensor provided in the common line as the primary side pressure.

[0024] Such gas supply methods and programs for gas supply systems can achieve the same effects and advantages as the gas supply system of the present invention described above. [Effects of the Invention]

[0025] According to the present invention configured in this manner, the uniformity of the surface temperature distribution of an object such as a wafer can be improved in a gas supply system for an electrostatic chuck device, and the number of parts can be reduced, thereby lowering manufacturing costs. [Brief explanation of the drawing]

[0026] [Figure 1] A schematic diagram showing the overall configuration of the electrostatic chuck device of this embodiment. [Figure 2] A schematic cross-sectional view showing the configuration of the electrostatic chuck device of the same embodiment. [Figure 3] A schematic perspective view showing the configuration of the electrostatic chuck and cooling section of the same embodiment. [Figure 4] A plan view showing the adsorption region set on the adsorption surface of the same embodiment. [Figure 5] A schematic diagram showing the configuration of the gas supply system in the same embodiment. [Figure 6] A functional block diagram showing the configuration of the control device of the same embodiment. [Figure 7] A schematic diagram showing the configuration of a gas supply system in another embodiment. [Figure 8] A schematic diagram showing the configuration of a gas supply system in another embodiment. [Figure 9] A plan view showing the adsorption region set on the adsorption surface of another embodiment. [Figure 10] A plan view showing the adsorption region set on the adsorption surface of another embodiment. [Figure 11] A plan view showing the adsorption region set on the adsorption surface of another embodiment. [Explanation of Symbols]

[0027] 100...Electrostatic Chuck Device D...Adsorption area 3. Gas supply system 31 ···Common Line 32...Gas supply line 331...Flow rate calculation section 41 ···First pressure sensor 42 ···Second pressure sensor 44 ···First flow resistance element W...wafer (object) S...Adsorption surface G...Space [Modes for carrying out the invention]

[0028] An embodiment of an electrostatic chuck device equipped with a gas supply system according to the present invention will be described below with reference to the drawings.

[0029] As shown in Figure 1, the electrostatic chuck device 100 of this embodiment is used for electrostatically adsorbing a wafer W to be processed, for example, in a vacuum chamber C of a semiconductor manufacturing apparatus using plasma. Specifically, as shown in Figures 1 and 2, the electrostatic chuck device 100 comprises an electrostatic chuck unit 1 having an adsorption surface 111 for electrostatically adsorbing the wafer W, a cooling unit 2 having a cooling surface 211 for cooling the electrostatic chuck unit 1, and a gas supply system 3 for supplying a thermally conductive gas to the space G between the adsorption surface 111 of the electrostatic chuck unit 1 and the adsorption surface S of the wafer W. The vacuum chamber C is configured to be evacuated by a vacuum pump (not shown).

[0030] As shown in Figures 2 to 4, the electrostatic chuck unit 1 comprises a circular, flat suction plate 11 made of an insulator such as ceramics or glass, an internal electrode 12 embedded in the suction plate 11, and a power supply 13 for applying a voltage to the internal electrode 12. By applying a voltage to the internal electrode 12 with the power supply 13, a dielectric polarization phenomenon occurs within the suction plate 11, and the upper surface 111 of the suction plate 11 becomes a generally planar suction surface. The electrostatic chuck unit 1 in this embodiment is a bipolar type, but it is not limited to a bipolar type and may also be a unipolar type. The upper surface 111 is, for example, embossed, and has an uneven surface shape.

[0031] As shown in Figures 3 and 4, the adsorption surface 111 of the adsorption plate 11 has multiple gas supply ports 3a for blowing out a thermally conductive gas. Each gas supply port 3a is formed to be rotationally symmetric, for example, with respect to the rotation axis of the adsorption plate 11. In this embodiment, the multiple gas supply ports 3a are formed in concentric rows (two rows in this case), and in each row they are formed to be approximately equally spaced from one another along the circumferential direction.

[0032] As shown in Figure 4, the adsorption surface 111 is divided radially (like a pizza cut) into multiple adsorption regions D (six in this case) of three or more. A thermally conductive gas, with its flow rate and pressure individually adjusted for each region, is supplied to the space G from a gas supply port 3a provided in each adsorption region D.

[0033] Each gas supply port 3a is formed by a through-hole 113 provided so as to penetrate the adsorption plate 11 in the thickness direction. This through-hole 113 has a diameter (inner diameter) of several micrometers to several tens of micrometers (for example, 0.03 mm) and a length (dimension along the axial direction) of several millimeters (for example, 2 mm), but these dimensions can be changed as appropriate.

[0034] As shown in Figures 2 and 3, the cooling unit 2 comprises a circular, flat metal base plate 21, a refrigerant flow path 212 formed within the base plate 21, and a refrigerant flow mechanism (not shown), such as a chiller, for circulating refrigerant through the refrigerant flow path 212. By circulating refrigerant through the refrigerant flow path 212 via the refrigerant flow mechanism, the temperature of the entire base plate 21 decreases, and the upper surface 211 of the base plate 21 becomes a roughly planar cooling surface. The adsorption plate 11 is placed on the base plate 21 such that its lower surface 112 (back surface) is in surface contact with the cooling surface 211 of the base plate 21. The refrigerant flow path 212 is formed inside the base plate 21 along a direction parallel to the cooling surface 211.

[0035] The gas supply system 3 supplies a thermally conductive gas to space G. Specifically, as shown in Figure 5, the gas supply system 3 comprises a common line 31 through which the thermally conductive gas flows, a plurality of parallel gas supply lines 32 whose upstream ends are connected to the common line 31, a plurality of leak lines 34 branching from each gas supply line 32, and a control device 33. The thermally conductive gas may be a single gas such as helium or argon, or any mixed gas obtained by mixing multiple gases in any ratio.

[0036] The common line 31 has a gas supply source (not shown) connected to its upstream side and introduces a thermally conductive gas into each gas supply line 32. The common line 31 is equipped with a fluid control valve 40 and a first pressure sensor 41 for measuring the pressure of the thermally conductive gas introduced into each gas supply line 32. In other words, this first pressure sensor is common to all gas supply lines 32. This first pressure sensor 41 is configured to measure the pressure of the thermally conductive gas passing through it, as well as its temperature.

[0037] The fluid control valve 40 changes the flow rate of the thermally conductive gas flowing through the common line 31 by changing its valve opening in response to a control signal from the control device 33. Examples of such valves include piezo actuator valves, solenoid actuator valves, and thermal actuator valves.

[0038] Each gas supply line 32 (connection point P with common line 31) JThe lines from the first to the gas supply port 3a are provided corresponding to each adsorption region D set on the adsorption surface 111. In this embodiment, all of the multiple gas supply lines 32 are connected to a common line 31, and each gas supply line 32 is configured to supply the thermally conductive gas introduced from the common line 31 to the space G from the gas supply port 3a of each adsorption region D. Specifically, each gas supply line 32 has a through-flow channel 321 (which is the "gas supply channel" in the claims) that penetrates the adsorption plate 11 in the thickness direction at its downstream end. This through-flow channel 321 is made up of the through-hole 113 described above, and its downstream end is in communication with the gas supply port 3a.

[0039] Each gas supply line 32 is equipped with a first flow resistance element 44, a second pressure sensor 42, a fluid control valve 46, a third pressure sensor 43, and a second flow resistance element 45, in that order from upstream.

[0040] The first flow resistance element 44 acts as a resistance when a thermally conductive gas flows, and has an inherent flow characteristic in which the mass flow rate of the gas passing through is determined based on the primary pressure, the secondary pressure, and the gas temperature, and is, for example, a laminar flow element resistor.

[0041] The second pressure sensor 42 measures the pressure of the thermally conductive gas (secondary pressure) downstream of the first flow resistance element 44. This second pressure sensor 42 is configured to measure the pressure of the passing thermally conductive gas as well as its temperature.

[0042] The fluid control valve 46 changes the flow rate of the heat-conducting gas passing through it by changing its valve opening in response to a control signal from the control device 33. Examples of such valves include piezo actuator valves, solenoid actuator valves, and thermal actuator valves.

[0043] The third pressure sensor 43 measures the pressure of the thermally conductive gas downstream of the fluid control valve 46. This third pressure sensor 43 is configured to measure the pressure of the thermally conductive gas passing through it, as well as its temperature.

[0044] The second flow resistance element 45 is provided in the through-flow channel 321 of the gas supply line 32 (more specifically, the portion that penetrates the adsorption plate 11). This second flow resistance element 45 acts as a resistance when the thermal conductive gas flows, and has a unique flow characteristic in which the mass flow rate of the gas passing through is determined based on the primary pressure, the secondary pressure, and the temperature of the gas. Here, the flow rate of the thermal conductive gas passing through the second flow resistance element 45 is determined based on the pressure of the thermal conductive gas in the gas supply line 32 (primary pressure), the pressure of the thermal conductive gas in space G (secondary pressure; hereinafter also referred to as wafer back surface pressure), and the temperature of the thermal conductive gas passing through it.

[0045] The second flow resistance element 45 in this embodiment is a laminar flow element resistor and, as shown in Figure 3, is composed of a flow path forming member 5 having a resistive flow path (resistive flow path) 51. This flow path forming member 5 is, for example, cylindrical, and its diameter (outer diameter) and length (dimension along the axial direction) are substantially the same as the diameter (inner diameter) and length of the through holes 113 of the suction plate 11. Each flow path forming member 5 is fitted snugly into each through hole 113 of the suction plate 11 with a fitting tolerance. The flow path forming member 5 may be made of any insulating material, such as ceramic. Preferably, the downstream end face of this second flow resistance element 45 is provided flush with the suction surface 111 of the suction plate 11. In this embodiment, the second flow resistance element 45 is provided in all of the multiple through holes 113 formed in the suction plate 11. The first flow resistance element 44 described above is configured similarly.

[0046] Each leak line 34 branches off from the gas supply line 32 downstream of the fluid control valve 46 (more specifically, downstream of the third pressure sensor 43). Each leak line 34 is configured to be exhausted by a vacuum pump 344 via a third flow resistance element 342. This third flow resistance element 342 acts as resistance when a thermally conductive gas flows through it and has a unique flow characteristic that determines the mass flow rate of the gas passing through it based on the primary pressure, secondary pressure, and gas temperature; for example, it is a laminar flow element resistor. Each leak line 34 is also provided with a bypass line 341 that branches off upstream of the third flow resistance element 342 and merges downstream of the third flow resistance element 342. This bypass line 341 is provided with an on-off valve 343 that switches between open and closed according to a control signal from the control device 33. This on-off valve 343 is, for example, an air valve, a piezo actuator valve, a solenoid actuator valve, a thermal actuator valve, etc.

[0047] The control device 33 is a general-purpose or dedicated computer that incorporates a CPU, internal memory, etc. Based on a predetermined program stored in its internal memory, the CPU and its peripheral devices cooperate to perform at least the functions of a flow rate calculation unit 331, a pressure calculation unit 332, a storage unit 333, a diagnostic unit 334, a flow rate target setting unit 335, and a valve control unit 336, as shown in Figure 6.

[0048] The flow rate calculation unit 331 individually calculates the flow rate of the thermally conductive gas introduced from the common line 31 to each gas supply line 32.

[0049] Specifically, the flow rate calculation unit 331 calculates the mass flow rate Q of the thermally conductive gas introduced from the common line 31 to each gas supply line 32, based on the inherent flow rate characteristics of the first flow resistance element 44, the primary side pressure P1 of the first flow resistance element 44, and the secondary side pressure P2 of the first flow resistance element 44. in It is configured to calculate this mass flow rate Q. inis the mass flow rate of the thermally conductive gas passing through the first flow rate resistance element 44 provided in each gas supply line 32. More specifically, the flow rate calculation unit 331 calculates the mass flow rate Q in based on the following formula (1) showing the relationship between the unique flow rate characteristics of each first flow rate resistance element 44 and its primary side pressure and secondary side pressure.

[0050]

Equation

[0051] In formula (1), f res1 : a function indicating the flow rate characteristics of the first flow rate resistance element 44, P1: the primary side (upstream side) pressure applied to the first flow rate resistance element 44, P2: the secondary side (downstream side) pressure applied to the first flow rate resistance element 44, T in : the temperature of the thermally conductive gas passing through the first flow rate resistance element 44 (here, it is considered equal to the temperature of the thermally conductive gas passing through the second pressure sensor 42).

[0052] The flow rate calculation unit 331 acquires the primary side pressure P1 from the first pressure sensor 41, acquires the secondary side pressure P2 and the temperature T of the thermally conductive gas in from the second pressure sensor 42, acquires the flow rate characteristic function f res1 from the storage unit 333, and is configured to calculate the mass flow rate Q in based on these information and formula (1). The flow rate characteristic function f res1 pre-stored in the storage unit 333 is, for example, a map or the like represented by a function having the primary side pressure P1 applied to the first flow rate resistance element 44, the secondary side pressure P2 applied to the first flow rate resistance element 44, and the temperature T in of the thermally conductive gas passing through the first flow rate resistance element as input variables and the mass flow rate passing through the first flow rate resistance element as an output variable.

[0053] Also, the flow rate calculation unit 331 of the present embodiment is configured to calculate the mass flow rate of the thermally conductive gas exhausted from each leak line 34.

[0054] Specifically, the flow rate calculation unit 331 calculates the flow rate based on the inherent flow rate characteristics of the third flow resistance element 342, the primary side pressure P3 of the third flow resistance element 342, and the secondary side pressure P of the third flow resistance element 342. VAC Based on this, the mass flow rate Q of the thermally conductive gas exhausted from each leak line 34 VAC It is configured to calculate this mass flow rate Q individually. VAC Q is the mass flow rate of the thermally conductive gas passing through the third flow resistance element 342 provided in each leak line 34. More specifically, the flow rate calculation unit 331 calculates the mass flow rate Q based on the following equation (2), which shows the relationship between the inherent flow characteristics of the third flow resistance element 342 and its primary and secondary pressures. VAC Calculate.

[0055]

number

[0056] In equation (2), f res3 : A function showing the flow characteristics of the third flow resistance element 342, P3: Primary side (upstream side) pressure applied to the third flow resistance element 342, P VAC : Secondary (downstream) pressure applied to the third flow resistance element 342, T VAC : This is the temperature of the thermally conductive gas passing through the third flow resistance element 342. Note that the secondary pressure P is... VAC The value may be a value measured by a pressure gauge (not shown) located downstream of the third flow resistance element 342 in the leak line 34, or it may be any value (for example, 0 Pa) that has been set in advance and stored in the memory unit 333. Also, temperature T VAC The value may be the value measured by a thermometer 344 installed on the leak line 34, or it may be considered to be equal to the temperature of the thermally conductive gas passing through the third pressure sensor 43.

[0057] The flow rate calculation unit 331 calculates the primary pressure P3 and the temperature T of the thermally conductive gas. VAC The flow characteristic function f is obtained from the third pressure sensor 43. res3 and secondary pressure P VAC The mass flow rate Q is obtained from the storage unit 333, and based on this information and equation (2),VAC It is configured to calculate the flow characteristic function f that is pre-stored in the memory unit 333. res3 For example, the primary pressure P3 applied to the third flow resistance element 342 and the secondary pressure P applied to the third flow resistance element 342 VAC The temperature T of the thermally conductive gas passing through the third flow resistance element 342 VAC This is a map, etc., represented by a function that takes and as input variables and the mass flow rate passing through the third flow resistance element 342 as the output variable.

[0058] The pressure calculation unit 332 individually calculates the pressure of the thermally conductive gas in each of the multiple regions set to radially divide the space G between the adsorption surface 111 and the surface to be adsorbed S (i.e., the wafer back surface pressure in each adsorption region D).

[0059] Specifically, this pressure calculation unit 332 calculates the mass flow rate Q of the thermally conductive gas supplied from the gas supply port 3a. ESC Based on the primary side pressure P3 of the second flow resistance element 45 and the inherent flow characteristics of the second flow resistance element 45, the wafer back surface pressure P in each region is determined. wafer It is configured to calculate the mass flow rate Q. ESC This is the mass flow rate of the thermally conductive gas passing through the through-channel 321 of the gas supply line 32, and in this embodiment, where a second flow resistance element 45 is provided in the through-channel 321, it is the mass flow rate of the thermally conductive gas passing through the second flow resistance element 45.

[0060] More specifically, the pressure calculation unit 332 calculates the mass balance of the mass flow rate of the thermal conductive gas flowing through the gas supply line 32 (i.e., the balance between the amount of thermal conductive gas entering the gas supply line 32 and the amount of thermal conductive gas leaving the gas supply line 32) using the following equation (3) and the mass flow rate Q of the thermal conductive gas introduced into the gas supply line 32. in Based on this, the mass flow rate Q of the thermally conductive gas supplied from the gas supply port 3a ESC It is configured to calculate the mass flow rate Q of the thermally conductive gas. The pressure calculation unit 332 then calculates the mass flow rate Q of the thermally conductive gas. ESCBased on the following equation (4), which shows the relationship with the intrinsic flow characteristics of the second flow resistance element 45, the wafer back surface pressure P wafer It is configured to calculate [the result].

[0061]

number

[0062] In equation (3), Q in : Mass flow rate of the thermally conductive gas introduced into the gas supply line 32, Q VAC : Mass flow rate of thermally conductive gas exhausted from leak line 34, (V / Z·R u ·T gas )·(dP / dt): Mass flow rate Q of thermally conductive gas leaking into the chamber from between the adsorption plate 11 and the wafer W. LEAK , V: Volume of the flow path between the fluid control valve 46 and the second flow resistance element 45 in the gas supply line 32. Z: Compressibility coefficient of the gas (here, Z=1) R u : Gas constant (8.3145 J·mol) -1 ·K -1 ), T gas : The average temperature of the heat-conducting gas in the flow path from the fluid control valve 46 to the second flow resistance element 45 in the gas supply line 32. dP / dt: Time change of the pressure of the thermally conductive gas in the flow path from the fluid control valve 46 to the second flow resistance element 45 in the gas supply line 32. That is the case. Furthermore, considering that the surface properties (e.g., shape, roughness, etc.) of the adsorption surface 111 of the adsorption plate 11 are not uniform within the plane, and that the heat energy exchange during the process is not stable, even after a sufficient amount of time has elapsed since the start of supplying the heat conductive gas by the gas supply line 32, the mass flow rate Q LEAK This does not result in a stable state (steady state), and dP / dt may not be zero.

[0063] Here, the pressure calculation unit 332 calculates the mass flow rate Q from the flow rate calculation unit 331. in and mass flow rate Q VAC The average temperature T is obtained from the third pressure sensor 43 installed in the gas supply line 32. gas The volume V of the flow path, the compressibility coefficient Z, and the gas constant R are obtained. u The mass flow rate Q of the thermal conductive gas supplied from the gas supply port 3a is obtained from the storage unit 333 and based on this information and equation (3), the mass flow rate Q of the thermal conductive gas is obtained. ESC It is configured to calculate [the result].

[0064]

number

[0065] In equation (4), f res2 : A function showing the flow characteristics of the second flow resistance element 45, P3: Primary side (upstream side) pressure applied to the second flow resistance element 45, P wafer : Wafer back surface pressure (secondary side pressure applied to the second flow resistance element 45), T ESC : This is the temperature of the thermally conductive gas passing through the second flow resistance element 45 (here, it is considered to be equal to the temperature of the adsorption plate 11).

[0066] The pressure calculation unit 332 acquires the primary pressure P3 from the third pressure sensor 43 and the temperature T of the thermally conductive gas from the optical fiber thermometer 47 that measures the temperature of the adsorption plate 11. ESC Obtain the flow characteristic function f res2 The wafer back surface pressure P is obtained from the storage unit 333, and based on this information and equation (4), the wafer back surface pressure P is obtained. wafer It is configured to calculate the flow characteristic function f that is pre-stored in the memory unit 333. res2 For example, the primary pressure P3 applied to the second flow resistance element 45 and the secondary pressure P applied to the second flow resistance element 45. wafer The temperature T of the thermally conductive gas passing through the second flow resistance element 45 ESC This is a map, etc., represented by a function that takes and as input variables and the mass flow rate passing through the second flow resistance element 45 as the output variable.

[0067] The diagnostic unit 334 diagnoses whether there are any abnormalities on the adsorption surface S of the wafer W. Specifically, this diagnostic unit 334 diagnoses the wafer back surface pressure P in each adsorption region D calculated by the pressure calculation unit 332. wafer And a predetermined pressure P stored in advance in the memory unit 333 s The system is configured to diagnose the presence or absence of abnormalities on the adsorption surface S of the wafer W by comparing it with the following: For example, the wafer back surface pressure P in each adsorption region D. wafer and pressure P s If the absolute value of the difference between this and is greater than or equal to a predetermined value, it is diagnosed that an abnormality has occurred on the adsorption surface S of the wafer W; if it is less than or equal to the predetermined value, it is diagnosed as normal. Note that this pressure P s This is set appropriately according to the details of the vacuum treatment applied to the wafer W.

[0068] The diagnostic unit 334 may be configured to diagnose the presence or absence of localized warping along the circumferential direction as an abnormality on the adsorption surface S of the wafer W. Specifically, the diagnostic unit 334 delivers a constant mass flow rate Q to each radially divided adsorption region D. ESC The wafer back surface pressure P in each adsorption region D when a thermally conductive gas is supplied. wafer The distribution of the wafer may be used to diagnose whether or not the wafer W is warped. For example, the wafer back surface pressure P in each adsorption region D. wafer By comparing this with a predetermined pressure reference value pre-stored in the memory unit 333, it may be determined that local warping has occurred (or has not occurred) in the wafer W.

[0069] The diagnostic unit 334 may also be configured to calculate the amount of warpage of the wafer W in each adsorption region D. For example, the diagnostic unit 334 calculates the mass flow rate Q of the thermally conductive gas supplied to each adsorption region D. ESC and wafer back surface pressure P wafer Based on this, the conductance in each adsorption region D may be calculated, and based on this conductance, the amount of warping of the wafer W in each adsorption region D may be calculated. For example, the diagnostic unit 334 may use the conductance value (or mass flow rate Q) which has been determined in advance by experiment or the like. ESC and wafer back surface pressure P waferThe amount of warpage in each adsorption region D may be calculated using table data showing the relationship between the conductance (or mass flow rate Q). The diagnostic unit 334 also calculates the amount of warpage in each adsorption region D using table data showing the relationship between the conductance (or mass flow rate Q). ESC and wafer back surface pressure P wafer The system may be configured to estimate the amount of warpage of each adsorption region D using a machine learning model that calculates the correlation between the adsorption region and the amount of warpage using machine learning.

[0070] Then, the flow rate target setting unit 335 sets the wafer back surface pressure P in each region calculated by the pressure calculation unit 332. wafer The flow rate target value Q introduced into each gas supply line 32 is set to a value within a predetermined range. t The system is configured to set the target flow rate and transmit it to the valve control unit 336. Specifically, the flow rate target setting unit 335 sets the wafer back surface pressure P in each region calculated by the pressure calculation unit 332. wafer The target value P is pre-stored in the memory unit 333. t By comparing these values, and based on a predetermined relational expression calculated in advance through experiments or simulations, the flow rate target value Q for each gas supply line is determined so that the absolute value of the difference falls within a predetermined range. t It is configured to set this.

[0071] The valve control unit 336 transmits control signals to each fluid control valve 46 and controls the valve opening. Specifically, the valve control unit 336 controls the mass flow rate Q calculated by the flow rate calculation unit 331. in Then, the flow rate target setting unit 335 sets the target value Q. t The flow rate calculation unit 331 calculates the mass flow rate Q by comparing it with the above. in The target value Q t The opening degree of the fluid control valve 46 is controlled by feedback to match the specified parameters.

[0072] With the electrostatic chuck device 100 of this embodiment configured in this way, the flow rate of thermally conductive gas flowing through the gas supply line 32 corresponding to each region radially divided between the adsorption surface 111 and the surface to be adsorbed S can be determined. By controlling this flow rate, the wafer back surface pressure P in each region can be controlled. waferThis allows for control and improvement of the uniformity of the surface temperature distribution of the wafer W. Here, instead of individually providing the first pressure sensor 41, which measures the primary side pressure of the first flow resistance element 44 necessary for calculating the flow rate of the thermally conductive gas flowing through each gas supply line 32, for each gas supply line 32, it is provided on a common line 31 and standardized, thereby reducing the number of parts and lowering manufacturing costs.

[0073] However, the present invention is not limited to the embodiments described above.

[0074] For example, the gas supply system 3 of another embodiment may include a second gas introduction line 35, as shown in Figure 7. The second gas introduction line 35 is connected to a gas supply source (not shown) on its upstream side and is for introducing a second gas, different from the thermally conductive gas, into each gas supply line 32. Examples of the second gas include inert gases such as nitrogen or argon, or CF4. This second gas introduction line 35 is connected to the upstream side of the first flow resistance element 44 in each gas supply line 32 and is common to all gas supply lines 32. The second gas introduction line 35 is provided with a fourth pressure sensor 48 for measuring the pressure of the second gas introduced into each gas supply line 32. This fourth pressure sensor 48 is configured to measure the pressure of the passing second gas and also to measure its temperature.

[0075] In this case, the flow rate calculation unit 331 calculates the mass flow rate Q of the second gas introduced from the second gas introduction line 35 to each gas supply line 32 based on the inherent flow rate characteristics of the first flow resistance element 44, the primary side pressure P4 of the first flow resistance element 44, and the secondary side pressure P2 of the first flow resistance element 44. cl It is configured to calculate the mass flow rate Q. cl The specific calculation method is the mass flow rate Q of the thermally conductive gas mentioned above. in The calculation method is the same as for [another calculation].

[0076] In another embodiment, the electrostatic chuck device 100 may not have a leak line 34 in the gas supply system 3, as shown in Figure 8. In this case, the pressure calculation unit 332 calculates “Q” in the above formula (3). VAC P = 0 wafer It is configured to calculate [something].

[0077] Furthermore, in the above embodiment, the second flow resistance element 45 was provided in all of the multiple through holes 113, but this is not limited to this. In other embodiments, the second flow resistance element 45 may be provided in only some of the multiple through holes 113.

[0078] Furthermore, in the above embodiment, the first flow resistance element 44, the second flow resistance element 45, and the third flow resistance element 342 were laminar flow element resistors, but the system is not limited to these. The first flow resistance element 44, the second flow resistance element 45, and the third flow resistance element 342 can be any resistor, as long as they have a flow characteristic in which the flow rate of the heat-conductive gas passing through is determined by the primary side pressure and the secondary side pressure.

[0079] Furthermore, the first flow resistance element 44, the second flow resistance element 45, and the third flow resistance element 342 do not have to be resistors provided within the flow path of the gas supply line 32. The first flow resistance element 44, the second flow resistance element 45, and the third flow resistance element 342 may be, for example, the flow path itself of the gas supply line 32, whose flow characteristics are known. Even in such cases, by utilizing the flow characteristics of the flow path, it is possible to determine the mass flow rate of the thermally conductive gas introduced into each gas supply line 32 and the back surface pressure of the wafer in each adsorption region.

[0080] Furthermore, in the above embodiment, all of the multiple gas supply lines 32 were connected to the common line 31, but this is not limited to that. In other embodiments, only some (two or more) of the multiple gas supply lines 32 may be connected to the common line 31.

[0081] Furthermore, in the above embodiment, the common line 31 was connected to the upstream end of each gas supply line 32, but this is not limited to that. In other embodiments, the common line 31 may be connected to any position upstream of the first flow resistance element 44 in each gas supply line 32.

[0082] Furthermore, while the gas supply system 3 in the above embodiment was used in conjunction with the electrostatic chuck device 100, it is not limited to this. In other embodiments, the gas supply system 3 may be used in conjunction with a vacuum chuck device that adsorbs objects such as wafers by vacuum adsorption, and may supply a thermally conductive gas to the space between the adsorption surface of the vacuum chuck device and the adsorbed surface of the object.

[0083] Furthermore, in the gas supply system 3 of the above embodiment, multiple adsorption regions D were set by dividing the entire surface of the adsorption surface 111 radially (like a pizza cut), but this is not the only embodiment. In other embodiments, as shown in Figure 9, multiple (in this case, three) adsorption regions D1 to D3 are set on the adsorption surface 111 by dividing it into concentric circles. Then, the annular adsorption region may be further divided into multiple adsorption regions by dividing it radially. Here, the outermost annular adsorption region D3 is divided radially into multiple (for example, seven) adsorption regions. In this way, by controlling the flow rate of the thermally conductive gas flowing through each gas supply line 32 corresponding to the inner adsorption regions D1 and D2, the back surface pressure of the wafer in each region D1 and D2 can be controlled, thereby improving the uniformity of the surface temperature distribution of the target object such as the wafer W. Furthermore, by monitoring the pressure of the thermally conductive gas supplied from each gas supply line 32 corresponding to each adsorption region further divided from the outermost adsorption region D3, it is possible to detect the occurrence of local warping along the circumferential direction of the wafer W. Furthermore, the adsorption region inside the radially divided annular adsorption region D3 does not necessarily have to be divided into multiple concentric regions; as shown in Figure 10, only a single circular adsorption region D1 may be formed. Also, the radially divided annular adsorption region D3 does not necessarily have to be the outermost annular region; as shown in Figure 11, an additional annular adsorption region D4 may be set further outward from it.

[0084] Furthermore, the diagnostic unit 334 of the above embodiment has the wafer back pressure P in each region calculated by the pressure calculation unit 332. wafer Based on this, the diagnostic unit 334 was configured to diagnose abnormalities such as local warping of the wafer W, but is not limited to this. In other embodiments, the diagnostic unit 334 is configured to diagnose the mass flow rate Q of the thermal conductive gas supplied from each gas supply port 3a (i.e., each region set radially) calculated by the pressure calculation unit 332. ESC Based on this, it may be configured to diagnose abnormalities such as localized warping of the wafer W.

[0085] Furthermore, it goes without saying that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from its spirit. [Industrial applicability]

[0086] According to the present invention, in a gas supply system for an electrostatic chuck device, the uniformity of the surface temperature distribution of an object such as a wafer can be improved, and the number of parts can be reduced, thereby reducing manufacturing costs.

Claims

1. A gas supply system for an electrostatic chuck device that supplies a thermally conductive gas into the space between the adsorption surface of the electrostatic chuck device, which adsorbs an object by electrostatic force, and the adsorbed surface of the object, A plurality of gas supply lines that supply the thermally conductive gas to each of the plurality of regions set within the space, A common line connected to each of the aforementioned gas supply lines, which introduces the thermally conductive gas into each of the aforementioned gas supply lines, The system includes a flow rate calculation unit that calculates the flow rate of the thermally conductive gas introduced from the common line to each of the gas supply lines, The flow rate calculation unit calculates the flow rate of the thermally conductive gas introduced into each gas supply line based on the flow rate characteristics of the first flow resistance elements provided in each gas supply line, the primary side pressure of the first flow resistance elements, and the secondary side pressure of the first flow resistance elements. A pressure sensor for measuring the primary side pressure is provided on the common line. A second flow resistance element is provided downstream of the first flow resistance element in each of the aforementioned gas supply lines. A gas supply system for an electrostatic chuck device, further comprising a pressure calculation unit that calculates the pressure of the thermal conductive gas in each region based on the primary side pressure of the second flow resistance element, the flow rate of the thermal conductive gas passing through the second flow resistance element, and the flow characteristics of the second flow resistance element.

2. A fluid control valve is provided downstream of the first flow resistance element in each of the aforementioned gas supply lines. The gas supply system for an electrostatic chuck device according to claim 1, configured to provide feedback control of the opening degree of the fluid control valve based on the flow rate calculated by the flow rate calculation unit.

3. Each of the aforementioned gas supply lines is equipped with a gas supply channel that opens onto the adsorption surface, A gas supply system for an electrostatic chuck device according to claim 1 or 2, wherein the second flow resistance element is provided in the gas supply channel in each of the gas supply lines.

4. A gas supply system for an electrostatic chuck device according to any one of claims 1 to 3, wherein the pressure calculation unit calculates the flow rate of the thermal conductive gas passing through the second flow resistance element based on the flow rate calculated by the flow rate calculation unit and a relational expression showing the mass balance of the flow rate of the thermal conductive gas in the gas supply line.

5. A gas supply system for an electrostatic chuck device according to any one of claims 1 to 4, further comprising a diagnostic unit that compares the calculated pressure of the thermally conductive gas with a predetermined reference pressure to diagnose abnormalities in the pressure value of the thermally conductive gas in each region.

6. A gas supply system for an electrostatic chuck device according to any one of claims 1 to 5, which adjusts the flow rate of the thermal conductive gas introduced into each gas supply line so that the pressure of the thermal conductive gas calculated by the pressure calculation unit is within a predetermined range.

7. A gas supply system for an electrostatic chuck device according to any one of claims 1 to 6, wherein the plurality of regions are set by radially dividing the space.

8. A gas supply system for an electrostatic chuck device according to any one of claims 1 to 6, wherein the plurality of regions are set by dividing the space into concentric circles and further dividing the annular region radially.

9. A gas supply system for an electrostatic chuck device according to claim 7 or 8, referencing claim 5, wherein the diagnostic unit is configured to diagnose whether or not the object is warped based on the mass flow rate of the thermal conductive gas supplied to each of the radially divided regions, or the pressure of the thermal conductive gas in each of the radially divided regions.

10. A gas supply system for an electrostatic chuck device according to any one of claims 1 to 9, wherein the thermally conductive gas is helium gas.

11. The gas supply line further comprises a second gas introduction line connected upstream of the first flow resistance element in each of the aforementioned gas supply lines, which introduces a second gas different from the thermal conductive gas into each of the aforementioned gas supply lines. The flow rate calculation unit calculates the flow rate of the second gas introduced into each gas supply line based on the flow rate characteristics of the first flow resistance element, the primary side pressure of the first flow resistance element, and the secondary side pressure of the first flow resistance element. A gas supply system for an electrostatic chuck device according to any one of claims 1 to 10, wherein a pressure sensor for measuring the primary side pressure is provided in the second gas introduction line.

12. A gas supply method for supplying a thermally conductive gas to the space between the adsorption surface of an electrostatic chuck device that adsorbs an object by electrostatic force and the adsorbed surface of the object, The electrostatic chuck device comprises a plurality of gas supply lines that supply the thermal conductive gas to each of a plurality of regions set in the space, and a common line connected to each of the gas supply lines that introduces the thermal conductive gas to each of the gas supply lines. Based on the flow characteristics of the first flow resistance element provided in each of the gas supply lines, the primary side pressure of the first flow resistance element, and the secondary side pressure of the first flow resistance element, the flow rate of the thermally conductive gas introduced from the common line to each of the gas supply lines is calculated. As the primary side pressure, the measured value of the pressure sensor installed on the common line is used. A gas supply method for calculating the pressure of the thermal conductive gas in each region based on the primary side pressure of a second flow resistance element provided downstream of the first flow resistance element in each gas supply line, the flow rate of the thermal conductive gas passing through the second flow resistance element, and the flow characteristics of the second flow resistance element.

13. A program for a gas supply system that supplies a thermally conductive gas into the space between the adsorption surface of an electrostatic chuck device that adsorbs an object by electrostatic force and the adsorbed surface of the object, The electrostatic chuck device comprises a plurality of gas supply lines that supply the thermal conductive gas to each of a plurality of regions set in the space, and a common line connected to each of the gas supply lines that introduces the thermal conductive gas to each of the gas supply lines. A flow rate calculation unit calculates the flow rate of the thermally conductive gas introduced from the common line to each gas supply line based on the flow rate characteristics of the first flow resistance element provided in each gas supply line, the primary side pressure of the first flow resistance element, and the secondary side pressure of the first flow resistance element. The computer is made to function as a pressure calculation unit that calculates the pressure of the thermal conductive gas in each region based on the primary side pressure of the second flow resistance element provided downstream of the first flow resistance element in each gas supply line, the flow rate of the thermal conductive gas passing through the second flow resistance element, and the flow characteristics of the second flow resistance element. A program for a gas supply system in which the flow rate calculation unit uses the measured value of a pressure sensor installed on the common line as the primary side pressure.

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