Electrostatic chuck device, pressure calculation method and program

Abstract

This electrostatic chuck device chucks an object by electrostatic force and comprises: a chuck plate having a chuck surface for chucking the object; a gas supply line for supplying a thermally conductive gas to the interspace between the chuck surface and the surface-to-be-chucked of the object; and a pressure calculation unit for calculating the pressure of the thermally conductive gas in the interspace. The gas supply line is provided with a flow resistance element that becomes resistive when the thermally conductive gas flows. The pressure calculation unit calculates the pressure of the thermally conductive gas in the interspace on the basis of the primary side pressure of the flow resistance element, the flow of the thermally conductive gas passing through the flow resistance element, and the flow characteristics of the flow resistance element.

Description

[Technical field]

[0001] The present invention relates to an electrostatic chuck device that attracts an object by electrostatic force, a pressure calculation method, and a program. [Background technology]

[0002] Conventionally, in semiconductor manufacturing processes using plasma processing equipment such as plasma etching equipment and plasma CVD equipment, electrostatic chuck devices are used to fix samples such as silicon wafers in vacuum chambers. The 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 is fixed, and, for example, plasma heat applied to the silicon wafer is released to the base plate side to cool the wafer, thereby making the surface temperature distribution uniform.

[0003] Incidentally, there are minute irregularities on the chucking surface of the chucking plate and the attracted surface of the silicon wafer. Therefore, even when the silicon wafer is attracted by the electrostatic chuck device, a minute gap of about 10 μm in thickness is generated between the attracted surface and the attracted surface, and the efficiency of heat conduction is reduced due to the small physical contact area. Conventionally, multiple gas supply ports are provided on the chucking surface of the chucking plate, and a thermally conductive gas is supplied to the gap between the attracted surface of the silicon wafer and the chucking surface of the chucking plate, so that the plasma heat applied to the silicon wafer is efficiently released to the chucking plate side (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-053576 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the semiconductor manufacturing process using the above-mentioned plasma processing apparatus, in order to improve the precision of the processed dimensions of an object such as a wafer, it is required to improve the uniformity of the wafer surface temperature. Since the uniformity of the wafer surface temperature is largely dependent on the pressure of the thermally conductive gas applied to the wafer's attracted surface (hereinafter also referred to as the wafer back pressure), it is important to grasp the wafer back pressure in order to improve the precision of the wafer's processed dimensions. In addition, it is important to grasp the wafer back pressure in the semiconductor manufacturing process from the viewpoint of early detection of the occurrence of an abnormality such as a decrease in the stability of the chucking force of the electrostatic chuck device due to aging or the like, or a symptom thereof. However, conventionally, there has been no way to grasp the wafer back pressure when the object is attracted by the electrostatic chuck device.

[0006] The present invention has been made to solve the above problems, and has as its main object to make it possible to grasp the back surface pressure of a wafer in a semiconductor manufacturing process using an electrostatic chuck device. [Means for solving the problem]

[0007] That is, the electrostatic chuck device of the present invention is for adsorbing an object by electrostatic force, and comprises an adsorption plate having an adsorption surface for adsorbing the object, a gas supply line for supplying a thermally conductive gas to a gap between the adsorption surface and an adsorbed surface of the object, and a pressure calculation unit for calculating the pressure of the thermally conductive gas in the gap, wherein the gas supply line is provided with a flow resistance element that provides resistance to the flow of the thermally conductive gas, and the pressure calculation unit calculates the pressure of the thermally conductive gas in the gap based on the primary side pressure of the flow resistance element, the flow rate of the thermally conductive gas passing through the flow resistance element, and the flow characteristics of the flow resistance element.

[0008] In such a case, the wafer backside pressure can be calculated and understood by utilizing the flow characteristics of the flow resistance element installed in the gas supply line, i.e., the unique characteristics that show the relationship between the primary side pressure (e.g., the pressure in the gas supply line) and secondary side pressure (e.g., the wafer backside pressure) of the flow resistance element and the flow rate of the thermally conductive gas passing through it.

[0009] A specific aspect of the electrostatic chuck device is one in which the gas supply line includes a gas supply passage formed in the suction plate so as to open onto the suction surface, and the flow resistance element is provided in the gas supply passage.

[0010] In this case, the flow rate resistor is provided in the gas supply passage that opens to the suction surface of the suction plate, so that the wafer back surface pressure can be calculated more accurately.

[0011] This "flow resistance element" may be any element having flow characteristics in which the flow rate of the thermally conductive gas passing through is determined by the pressure on the primary side and the pressure on the secondary side, but a laminar flow element resistor is particularly preferred. Since the laminar flow element resistor has excellent processing accuracy and excellent reproducibility, by using the laminar flow element resistor as the flow resistance element, the pressure of the thermally conductive gas in the gap between the attracting surface and the attracted surface can be calculated with higher accuracy. In addition, since the laminar flow element resistor has a high degree of design freedom, the degree of freedom of the outer diameter of the thermally conductive gas outlet can be increased, and the occurrence of arc discharge can be suppressed.

[0012] A specific example of the pressure calculation unit is one configured to calculate the flow rate of the thermally conductive gas passing through the flow resistance element based on the flow rate of the thermally conductive gas introduced into the gas supply line and a relational equation showing the material balance of the flow rate of the thermally conductive gas in the gas supply line.

[0013] A specific embodiment of the electrostatic chuck device includes an electrostatic chuck device further comprising a pressure controller equipped with a flow sensor and configured to measure and control the pressure of the thermally conductive gas in the gas supply line, wherein the pressure calculation unit calculates the pressure of the thermally conductive gas in the gap by using the pressure value measured by the pressure controller as the primary side pressure of the flow resistance element and the flow rate value measured by the flow sensor as the flow rate value of the thermally conductive gas introduced into the gas supply line.

[0014] Another specific aspect of the electrostatic chuck device is one further comprising a pressure type flow controller that measures and controls a flow rate of the thermally conductive gas flowing through the gas supply line, and the pressure calculation unit calculates the pressure of the thermally conductive gas in the gap using the pressure value measured by the pressure type flow controller as the primary side pressure of the flow resistance element and the flow rate value measured by the pressure type flow controller as the flow rate value of the thermally conductive gas introduced into the gas supply line.

[0015] In order to be able to diagnose the presence or absence of an abnormality on the back surface of the wafer during plasma processing, such as a decrease in the adsorption force on the wafer due to deterioration of the device over time, the electrostatic chuck device may further include a diagnosis unit that compares the calculated pressure of the thermally conductive gas with a predetermined reference pressure to diagnose an abnormality in the pressure value of the thermally conductive gas applied to the adsorbed surface.

[0016] It is preferable that the electrostatic chuck device is configured to adjust the pressure of the thermally conductive gas in the gas supply line so that the calculated pressure of the thermally conductive gas is within a predetermined range.

[0017] It is preferable that the electrostatic chuck device is configured to adjust the flow rate of the thermally conductive gas flowing through the gas supply line so that the calculated pressure of the thermally conductive gas is within a predetermined range.

[0018] It is preferable that the electrostatic chuck device has a plurality of the gas supply lines, each of which is configured to supply the thermally conductive gas to a different region between the attracting surface and the attracted surface. In this way, the pressure applied to the rear surface of the wafer can be adjusted for each region.

[0019] In a specific embodiment of the electrostatic chuck device, the gas supply line is configured to be able to supply a plurality of types of the thermally conductive gases at any mixing ratio. In this way, by using a mixture of multiple types of thermally conductive gas, the amount of expensive gas (for example, helium gas) used can be reduced, thereby reducing costs.

[0020] The electrostatic chuck device also calculates a flow rate Q of the thermally conductive gas leaking from the gap based on a time change in pressure of the thermally conductive gas in the gas supply line. LEAK In this case, the electrostatic chuck device may be configured to calculate the flow rate Q based on the following formula (a): LEAK It is preferable to calculate TIFF0007635243000001.tif11136 Where, V is the volume of the flow passage that constitutes the gas supply line, Z is the compression coefficient of the thermally conductive gas, and R u : Gas constant of thermally conductive gas, T gas : the temperature of the thermally conductive gas flowing through the gas supply line, and dP / dT: the time change in pressure of the thermally conductive gas in the gas supply line. With this configuration, it is possible to grasp the flow rate of the thermally conductive gas leaking from the gap between the electrostatic chuck device and the object to be attracted, and to grasp the degree of deterioration of the electrostatic chuck device, etc.

[0021] However, in the electrostatic chuck device described above, if the pressure of the thermally conductive gas supplied to the back surface of the wafer is too high, the wafer may be separated from the chucking surface. For this reason, in the conventional electrostatic chuck device, a leak line with a resistor is provided branching off from the gas supply line, and the excess thermally conductive gas is exhausted at a predetermined flow rate. On the other hand, this leak line is also used to exhaust the thermally conductive gas remaining in the gas supply line after the plasma processing is completed, but since the resistor is provided on the leak line, the thermally conductive gas cannot be immediately exhausted after the plasma processing is completed, and it takes time. As a result, when the plasma processing is completed and the electrostatic chuck device is switched to the dechuck state, the thermally conductive gas remaining in the gas supply line may flow into the vacuum chamber, generating a spark and causing the equipment to break down. Therefore, it is preferable that the electrostatic chuck device is configured to include a main leak line branched from the gas supply line and provided with a resistor, a bypass line provided to bypass the resistor, an on-off valve provided on the bypass line, and a valve control unit that controls the on-off valve, and is configured such that the flow resistance of the bypass line is smaller than the flow resistance of the main leak line. In this way, when the plasma processing is completed and the electrostatic chuck device is switched to the dechuck state, the on-off valve can be opened to immediately exhaust the thermally conductive gas through the bypass line, which has a relatively small flow resistance, thereby reducing the risk of sparks being generated by the thermally conductive gas flowing into the vacuum chamber immediately after the plasma processing is completed.

[0022] Furthermore, the pressure calculation method of the present invention is a pressure calculation method in an electrostatic chuck device that attracts an object by electrostatic force, the electrostatic chuck device comprising: an attraction plate having an attraction surface that attracts the object; and a gas supply line that supplies a thermally conductive gas to a gap between the attraction surface and an attracted surface of the object, the gas supply line being provided with a flow resistance element that provides resistance to the flow of the thermally conductive gas, and the pressure of the thermally conductive gas in the gap is calculated based on a primary side pressure of the flow resistance element, a flow rate of the thermally conductive gas passing through the flow resistance element, and a flow characteristic of the flow resistance element.

[0023] Furthermore, the pressure calculation program of the present invention is for recording a pressure calculation program for an electrostatic chuck device that attracts an object by electrostatic force, the electrostatic chuck device comprising an attraction plate having an attraction surface that attracts the object, and a gas supply line that supplies a thermally conductive gas to a gap between the attraction surface and an attracted surface of the object, the gas supply line being provided with a flow resistance element that provides resistance to the flow of the thermally conductive gas, and the pressure calculation program causes a computer to function as a pressure calculation unit that calculates the pressure of the thermally conductive gas in the gap based on a primary side pressure of the flow resistance element, a mass flow rate of the thermally conductive gas passing through the flow resistance element, and a flow characteristic of the flow resistance element.

[0024] Such a pressure calculation method and pressure calculation program can also achieve the same effects as those of the electrostatic chuck device of the present invention described above. Effect of the Invention

[0025] According to the present invention thus configured, it is possible to grasp the pressure on the back surface of a wafer during a semiconductor manufacturing process using an electrostatic chuck device. [Brief description of the drawings]

[0026] [Figure 1] 1 is a schematic diagram showing an overall configuration of an electrostatic chuck device according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a cross-sectional view illustrating a schematic configuration of the electrostatic chuck device according to the embodiment. [Diagram 3] FIG. 2 is a perspective view showing a schematic configuration of an electrostatic chuck unit and a cooling unit in the embodiment; [Figure 4] FIG. 2 is a perspective view showing a schematic configuration of an electrostatic chuck unit and a cooling unit in the embodiment; [Diagram 5] FIG. 2 is a diagram showing a schematic configuration of a gas supply unit of the embodiment. [Figure 6] FIG. 11 is a diagram illustrating a configuration of a gas supply unit according to another embodiment. [Figure 7] FIG. 11 is a diagram illustrating a configuration of a gas supply unit according to another embodiment. [Figure 8] FIG. 11 is a diagram illustrating a configuration of a gas supply unit according to another embodiment. [Figure 9] FIG. 11 is a diagram illustrating a configuration of a gas supply unit according to another embodiment. [Figure 10] FIG. 11 is a diagram illustrating a configuration of a gas supply unit according to another embodiment. [Explanation of symbols]

[0027] 100: Electrostatic chuck device 111...Adsorption surface 31 Gas supply line 31a Gas supply port 34 Flow resistance element W: Wafer (object) S...Adsorption surface G Gap DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] An embodiment of an electrostatic chuck device 100 according to the present invention will be described below with reference to the drawings.

[0029] 1, an electrostatic chuck device 100 according to the present embodiment is for electrostatically attracting a wafer W to be processed in a vacuum chamber C of a semiconductor manufacturing device using plasma, for example. Specifically, as shown in FIG. 2, the electrostatic chuck device 100 includes an electrostatic chuck unit 1 having an attracting surface 111 for electrostatically attracting the wafer W, a cooling unit 2 having a cooling surface 211 for cooling the electrostatic chuck unit 1, and a gas supply unit 3 for supplying a thermally conductive gas (also referred to as a backside gas) to a gap G between the attracting surface 111 of the electrostatic chuck unit 1 and an attracted surface S of the wafer W. The vacuum chamber C is configured to be evacuated by a vacuum pump V1.

[0030] 2 and 3, the electrostatic chuck unit 1 includes a circular flat chucking plate 11 made of an insulator such as ceramics or glass, an internal electrode 12 embedded in the chucking plate 11, and a power source 13 for applying a voltage to the internal electrode 12. When a voltage is applied to the internal electrode 12 by the power source 13, a dielectric polarization phenomenon occurs in the chucking plate 11, and an upper surface 111 of the chucking plate 11 becomes a substantially flat chucking surface. The electrostatic chuck unit 1 in this embodiment is of a bipolar type, but is not limited to this and may be of a monopolar type.

[0031] As shown in Figs. 2 to 4, the cooling unit 2 includes a metal base plate 21 having a circular flat plate shape, a refrigerant flow path 212 formed in the base plate 21, and a refrigerant flow mechanism (not shown) such as a chiller that flows a refrigerant through the refrigerant flow path 212. By flowing a refrigerant through the refrigerant flow path 212 by the refrigerant flow mechanism, the temperature of the entire base plate 21 is reduced, and the upper surface 211 of the base plate 21 becomes a roughly flat cooling surface. The adsorption plate 11 is placed on the base plate 21 so that its lower surface 112 (rear 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.

[0032] 5, the gas supply unit 3 includes a gas supply line 31 provided with a flow rate controller 32 for controlling the flow rate of the thermally conductive gas, a control device 33 for controlling the flow rate controller 32 and the like, and a leak line L branching off from the gas supply line 31. This thermally conductive gas may be any gas, such as helium gas, argon gas, or a mixed gas in which a plurality of gases are mixed at any ratio.

[0033] The gas supply line 31 is connected to a gas supply source (not shown) on the upstream side, and supplies a thermally conductive gas from a gas supply port 31a provided at the downstream end to a gap G between the suction surface 111 and the attracted surface S of the wafer W. This gas supply port 31a is formed in the suction surface 111 of the suction plate 11.

[0034] Specifically, this gas supply line 31 includes, from the downstream side, a first internal flow path (referred to as a gas supply flow path in the claims) 311 formed in the suction plate 11, a second internal flow path 312 formed in the base plate 21 so as to communicate with the first internal flow path 311, and a piping flow path (not shown) formed by piping that communicates with the second internal flow path 312 and connects between the base plate 21 and a gas supply source.

[0035] 2 and 4, a plurality of first internal flow paths 311 are formed so as to penetrate the suction plate 11 in the plate thickness direction and open onto the suction surface 111. The opening of each first internal flow path 311 on the suction surface 111 serves as a gas supply port 31a. Each gas supply port 31a is formed so as to be rotationally symmetrical with respect to the rotation axis of the suction plate 11 as the axis of symmetry, for example. In this embodiment, each first internal flow path 311 is formed in a plurality of concentric rows (two rows in this case) on the outer periphery of the suction plate 11, and is formed so as to be approximately equally spaced from each other along the circumferential direction in each row.

[0036] Specifically, each first internal flow path 311 is configured by a linear through-hole 113 having a circular cross section that penetrates the suction plate 11 in the plate thickness direction. This through-hole 113 has a diameter dimension (inner diameter) of about several μm to several tens of μm (e.g., 0.03 mm) and a length dimension (dimension along the axial direction) of about several mm (e.g., 2 mm), but these dimensions may be changed as appropriate.

[0037] The second internal flow passage 312 is formed to penetrate the base plate 21 in the plate thickness direction, with its upstream end opening to the lower surface of the base plate 21 and its downstream end opening to the upper surface (cooling surface) 211 of the base plate 21 and communicating with the first internal flow passage 311.

[0038] 2 and 3, a groove 213 is formed in the upper surface 211 of the base plate 21 along an in-plane direction, and at least a part of this groove 213 penetrates the base plate 21 in the plate thickness direction and opens to the lower surface. When the suction plate 11 is placed so as to cover this groove 213, a second internal flow path 312 is formed by the inner surface of the groove 213 and the lower surface 112 of the suction plate 11. This groove 213 is formed so as to pass directly below each through-hole 113 of the suction plate 11 when the suction plate 11 is placed on the base plate 21.

[0039] The flow rate controller 32 measures and controls the flow rate of the passing gas, and is provided in the piping flow path. A specific example of the flow rate controller 32 is a so-called pressure-type mass flow controller having a pressure sensor that measures the pressure of the passing gas, a flow rate sensor that measures the flow rate of the gas, a fluid control valve, and a valve controller that controls the aperture of the fluid control valve. The flow rate controller 32 feedback-controls the aperture of the fluid control valve, etc., so that the measured gas flow rate coincides with a target value set by the control device 33.

[0040] The control device 33 is a general-purpose or dedicated computer incorporating a CPU, an internal memory, etc. The control device 33 at least functions as a flow rate target setting unit 334 that sets a target value of the flow rate of the flow rate controller 32, as shown in FIG. 5, by the CPU and its peripheral devices working together based on a predetermined program stored in the internal memory.

[0041] The leak line L branches off from the gas supply line 31 at a position downstream of the flow rate controller 32. The leak line L is configured to be evacuated by a vacuum pump V2 via an arbitrary resistor R (e.g., an orifice or the like) that allows a constant flow rate of gas to pass through.

[0042] Thus, in the electrostatic chuck device 100 of the present embodiment, the flow rate resistive elements 34 are provided in all of the first internal flow passages 311 of the gas supply line 31 .

[0043] The flow resistance element 34 provides resistance when the thermally conductive gas flows, has a unique flow characteristic that determines the mass flow rate of the gas passing through it based on the primary pressure, the secondary pressure, and the gas temperature, and is a laminar flow element resistor in this embodiment. Here, the flow rate of the thermally conductive gas passing through the laminar flow element resistor 34 is determined based on the pressure of the thermally conductive gas in the gas supply line 31 (primary pressure), the pressure of the thermally conductive gas in the gap G between the adsorption surface 111 and the adsorbed surface S (secondary pressure, hereinafter also referred to as the wafer back pressure), and the temperature of the thermally conductive gas passing through it.

[0044] Specifically, the laminar flow element resistor 34 is composed of a flow path forming member 341 having a flow path (hereinafter also referred to as a resistance flow path) 341a that serves as a resistance. The flow path forming member 341 is cylindrical, and its diameter dimension (outer diameter) and length dimension (dimension along the axial direction) are approximately the same as the diameter dimension (inner diameter) and length dimension of the through hole 113 of the suction plate 11. As shown in FIG. 4, each flow path forming member 341 is fitted into each through hole 113 of the suction plate 11 without any gaps, with a fitting tolerance. The flow path forming member 341 may be composed of any insulating material such as ceramic. It is preferable that the downstream end face of the laminar flow element resistor 34 is provided so as to be flush with the suction surface 111 of the suction plate 11.

[0045] One or more resistance flow paths 341a are formed along the axial direction of the flow path forming member 341. Each resistance flow path 341a penetrates the flow path forming member 341 in the axial direction and is linear with a circular cross section, and examples of the resistance flow paths 341a include those formed on the axis of the flow path forming member 341 and those regularly arranged around the axis.

[0046] The electrostatic chuck device 100 of the present embodiment is characterized in that the control device 33 further fulfills the functions of a pressure calculation unit 331, a storage unit 332, and a diagnosis unit 333.

[0047] In the electrostatic chuck device 100 of the present embodiment, the pressure calculation unit 331 calculates the mass flow rate Q ESC Based on the primary pressure P1 of the laminar flow element resistor 34 and the inherent flow characteristics of the laminar flow element resistor 34, the wafer backside pressure P wafer The mass flow rate Q ESC is the mass flow rate of the thermally conductive gas passing through the first internal flow path 311 (through hole 113) formed in the suction plate 11, and in this embodiment in which a laminar flow element resistor 34 is provided in the through hole 113, is the mass flow rate of the thermally conductive gas passing through the laminar flow element resistor 34.

[0048] Specifically, the pressure calculation unit 331 calculates the mass flow rate Q of the thermally conductive gas introduced into the gas supply line 31 by calculating the mass flow rate Q of the thermally conductive gas introduced into the gas supply line 31 from the following relational expression (1) which indicates the material balance of the mass flow rate of the thermally conductive gas flowing through the gas supply line 31 (i.e., the balance between the amount of the thermally conductive gas entering the gas supply line 31 and the amount of the thermally conductive gas leaving the gas supply line 31). in Based on this, the mass flow rate Q of the thermally conductive gas supplied from the gas supply port 31a is ESC The pressure calculation unit 331 is configured to calculate the calculated mass flow rate Q of the thermally conductive gas. ESC and the inherent flow characteristic of the laminar flow element resistor 34, the wafer back surface pressure P wafer The method is configured to calculate

[0049]

number

[0050] In formula (1), Q in : mass flow rate of thermally conductive gas introduced into gas supply line 31, Q VAC : the mass flow rate of the thermally conductive gas exhausted from the leak line L and passing through the resistor R, (V / Z·R u T gas ) (dP / dT): Mass flow rate Q of the thermally conductive gas leaking into the chamber from between the chucking plate 11 and the wafer W LEAK , V: the volume of the flow path from the flow rate controller 32 to the laminar flow element resistor 34 in the gas supply line 31, Z: gas compressibility factor (here, Z=1), R u :Gas constant (8.3145 J·mol -1 ·K -1 ), T gas Average temperature of the thermal conduction gas in the flow path from the flow rate controller 32 to the laminar flow element resistor 34 in the gas supply line 31, dP / dt: the change over time in pressure of the thermally conductive gas in the flow path from the flow rate controller 32 to the laminar flow element resistor 34 in the gas supply line 31. In addition, 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 surface and that the heat energy exchange during the process is not stable, the mass flow rate Q LEAK may not be in a stable state (steady state) and dP / dt may not be zero.

[0051] Here, the pressure calculation unit 331 receives the mass flow rate Q in The average temperature T gas and obtain the mass flow rate of the leak gas Q VAC , the volume of the flow passage V, the compressibility factor Z and the gas constant R u is acquired from the storage unit 332, and the mass flow rate Q of the thermally conductive gas supplied from the gas supply port 31a is calculated based on this information and the formula (1). ESC The method is configured to calculate

[0052]

number

[0053] In formula (2), f res : Function showing the flow rate characteristics of the laminar flow element resistor 34, P1: Primary side (upstream side) pressure applied to the laminar flow element resistor 34, P wafer : Wafer back pressure (secondary pressure acting on laminar flow element resistor 34), T ESC : the temperature of the thermally conductive gas passing through the laminar flow element resistor 34 (here, considered to be equal to the temperature of the adsorption plate 11).

[0054] The pressure calculation unit 331 obtains the primary pressure P1 from the pressure measured by the flow rate controller 32, and obtains the temperature T of the thermally conductive gas from an optical fiber thermometer T2 that measures the temperature of the adsorption plate 11. ESC and obtain the flow characteristic function f resis obtained from the storage unit 332, and the wafer back surface pressure P wafer The flow characteristic function f res is, for example, the primary pressure P1 acting on the laminar flow element resistor 34 and the secondary pressure P wafer and the temperature T of the thermally conductive gas passing through the laminar flow element resistor 34. ESC and the like, which is expressed as a function having the mass flow rate passing through the laminar flow element resistor 34 as an output variable.

[0055] The diagnosis unit 333 diagnoses whether or not there is an abnormality in the attracted surface S of the wafer W. Specifically, the diagnosis unit 333 diagnoses whether or not there is an abnormality in the attracted surface S of the wafer W. wafer and a predetermined pressure P s For example, the wafer back pressure P wafer and pressure P s If the absolute value of the difference between the pressure P and the pressure P is equal to or greater than a predetermined value, it is determined that an abnormality has occurred on the attracted surface S of the wafer W, and if it is equal to or less than the predetermined value, it is determined that the surface is normal. s is appropriately set depending on the content of the vacuum processing for the wafer W.

[0056] The flow rate target setting unit 334 calculates the wafer back surface pressure P wafer The flow rate target value of the flow rate controller 32 is set so that the flow rate is within a predetermined range, and the flow rate target value is transmitted to the flow rate controller 32. Specifically, the flow rate target setting unit 334 is configured to set the flow rate target value of the flow rate controller 32 so that the flow rate is within a predetermined range, and transmit the flow rate target value to the flow rate controller 32. wafer and a target value P t and sets a flow rate target value based on a predetermined relational expression calculated in advance through experiments or simulations so that the absolute value of the difference falls within a predetermined range.

[0057] According to the electrostatic chuck device 100 of the present embodiment configured as described above, the first internal flow passage 311 communicating with the gas supply port 31a of the gas supply line 31 has a flow rate characteristic f res By providing a flow resistance element 34 whose flow characteristic f res The primary pressure P1 of the flow resistance element 34 is used to calculate the wafer back pressure P Wafer This contributes to improving the accuracy of the processing dimensions of the wafer W, and also makes it possible to grasp the occurrence and signs of an abnormality such as a decrease in the stability of the chucking force due to aging or the like. Furthermore, since the flow resistance element 34, which acts as a resistance when the thermally conductive gas flows, is provided in the first internal flow path 311 so as to block the gas supply port 31a, it is possible to prevent an excessive amount of thermally conductive gas from flowing out from the gas supply port 31a when dechucking the wafer W or cleaning the processing chamber.

[0058] The present invention is not limited to the above-described embodiment.

[0059] 6, an electrostatic chuck device 100 according to another embodiment may include a plurality of gas supply lines 31, and each gas supply line 31 may be configured to supply a thermally conductive gas to different regions between the chucking surface 111 of the chucking plate 11 and the attracted surface S of the wafer W. In this case, the chucking surface 111 of the chucking plate 11 may be divided into a plurality of gas supply regions corresponding to the number of the gas supply lines 31, and each gas supply line 31 may be configured to supply a thermally conductive gas individually from a gas supply port 31a provided in each gas supply region. The type, flow rate, and wafer backside pressure of the thermally conductive gas supplied from each gas supply line 31 may be set for each gas supply line 31.

[0060] In another embodiment of the electrostatic chuck device 100, the gas supply unit 3 does not need to include the leak line L, as shown in FIG. 7. In this case, the pressure calculation unit 331 calculates "Q VAC =0” as P wafer The method is configured to calculate:

[0061] In addition, the electrostatic chuck device 100 of the above embodiment is equipped with a pressure-type flow rate controller 32, but this is not limited to this. in and the pressure P1 of the thermally conductive gas in the gas supply line 31, the wafer back pressure P Wafer It is possible to grasp the following:

[0062] For example, as shown in FIG. 8, an electrostatic chuck device 100 according to another embodiment may be provided with a pressure controller 35 for measuring and controlling the pressure of the thermally conductive gas in the gas supply line 31, instead of the flow rate controller 32. A specific example of the pressure controller 35 includes a flow rate sensor, a fluid control valve, a pressure sensor, and a valve controller for feedback-controlling the opening of the fluid control valve based on the output of the pressure sensor. Even in such an embodiment, the pressure calculation unit 331 uses the pressure value measured by the pressure controller 35 as the primary side pressure P1 of the flow rate resistance element 34, and calculates the flow rate Q of the thermally conductive gas introduced into the gas supply line 31. in The wafer back pressure P wafer can be calculated.

[0063] Alternatively, instead of the flow rate controller 32, a mass flow rate Q of the thermal conductive gas introduced into the gas supply line 31 may be used as the flow rate controller as shown in FIG. in and a pressure gauge 37 that measures the pressure P1 of the thermally conductive gas in the gas supply line 31.

[0064] In the above embodiment, the flow resistance elements 34 are provided in all of the first internal flow paths 311, but this is not limited thereto. In other embodiments, the flow resistance elements 34 may be provided in only some of the first internal flow paths 311.

[0065] In the above embodiment, the flow resistance element 34 is provided in the first internal flow path 311, but this is not limited thereto. In other embodiments, the flow resistance element 34 may be formed in a flow path of the gas supply line 31 communicating with the gap G, such as the second internal flow path 312 or a piping flow path (not shown) connecting the base plate 21 and the gas supply source. In order to calculate the wafer backside pressure more accurately, the flow resistance element 34 is preferably provided further downstream in the gas supply line 31.

[0066] In addition, the flow resistance element 34 in the above embodiment is a laminar flow element resistor, but is not limited to this. The flow resistance element 34 may be any element as long as it has a flow characteristic in which the flow rate of the thermally conductive gas passing through it is determined by the pressure on the primary side and the pressure on the secondary side. Furthermore, the flow resistance element 34 does not have to be a resistor provided in the flow path of the gas supply line 31. The flow resistance element 34 may be, for example, the flow path itself (such as the first internal flow path 311) of the gas supply line 31, whose flow characteristics are known. Even in such a case, the wafer backside pressure can be grasped by utilizing the flow characteristics of the flow path.

[0067] The electrostatic chuck device 100 of another embodiment includes a resistance change mechanism 4 that changes the magnitude of the flow resistance of the leak line L to the thermal conductive gas. Specifically, as shown in FIG. 10, the resistance change mechanism 4 includes a bypass line 41 provided to bypass the resistor R in the leak line L, an on-off valve 42 provided on the bypass line 41, and a valve control unit 335 that controls the on-off valve 42. The bypass line 41 of this embodiment is provided to branch off from the leak line L on the upstream side of the resistor R and join the leak line L on the downstream side of the resistor R. When the on-off valve 42 is in an open state, the flow resistance (pipe resistance) of the bypass line 41 is set to be smaller than the flow resistance of the main leak line 43 in which the resistor R is provided. The on-off valve 42 is configured to be switched between open and closed in response to a control signal from the valve control unit 335, and is, for example, an air valve, a piezoelectric actuator valve, a solenoid actuator valve, a thermal actuator valve, or the like. The on-off valve 42 is normally closed (normally closed). The valve control unit 335 is a function exerted by the control device 33, and transmits a control signal to the on-off valve 42 to switch the on-off state. The valve control unit 335 of the present embodiment is configured to transmit a signal to the valve control unit 335 immediately upon receiving a signal indicating that the electrostatic chucking of the wafer by the electrostatic chuck unit 1 is to be released (dechucked) to open the valve control unit 335. The electrostatic chuck device 100 of the other embodiment includes such a resistance change mechanism 4, and thus can immediately exhaust the thermally conductive gas through the bypass line 41 when the electrostatic chuck unit 1 is switched to the dechuck state. This can reduce the risk of sparks occurring due to the outflow of the thermally conductive gas into the vacuum chamber C immediately after the plasma processing is completed.

[0068] In addition, when the electrostatic chuck device 100 includes the resistance change mechanism 4, the bypass line 41 may be configured to be exhausted by another vacuum pump without merging downstream of the resistor R. In addition, the bypass line 41 may not be provided so as to branch off upstream of the resistor R in the leak line L. For example, the bypass line 41 may be configured to branch off upstream or downstream of the branch point of the leak line L in the gas supply line 31. In addition, the bypass line 41 may be provided with any resistor, such as a flow resistance element. Even in such a case, if the flow resistance of the bypass line 41 is set to be smaller than the flow resistance of the main leak line 43, the thermally conductive gas can be immediately exhausted through the bypass line 41 when the electrostatic chuck unit 1 is switched to the dechuck state.

[0069] Furthermore, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible without departing from the spirit and scope of the present invention. [Industrial Applicability]

[0070] According to the electrostatic chuck device of the present invention, the pressure on the back surface of a wafer can be grasped in a semiconductor manufacturing process using the electrostatic chuck device.

Claims

1. An electrostatic chuck device that attracts an object by electrostatic force, an adsorption plate having an adsorption surface for adsorbing the object; a gas supply line for supplying a thermally conductive gas to a gap between the adsorption surface and an adsorbed surface of the object; a pressure calculation unit that calculates a pressure of the thermally conductive gas in the gap, a flow resistance element that acts as a resistance when the thermally conductive gas flows is provided in the gas supply line; An electrostatic chuck device, wherein the pressure calculation unit calculates the pressure of the thermally conductive gas in the gap based on the primary side pressure of the flow resistance element, the flow rate of the thermally conductive gas passing through the flow resistance element, and the flow characteristics of the flow resistance element.

2. the gas supply line includes a gas supply passage formed in the suction plate so as to open onto the suction surface; 2. The electrostatic chuck device according to claim 1, wherein the flow resistance element is disposed within the gas supply passage.

3. 3. The electrostatic chuck device according to claim 1, wherein the pressure calculation unit calculates the flow rate of the thermally conductive gas passing through the flow resistance element based on a flow rate of the thermally conductive gas introduced into the gas supply line and a relational equation indicating a material balance of the flow rate of the thermally conductive gas in the gas supply line.

4. a pressure controller including a flow rate sensor and configured to measure and control the pressure of the thermally conductive gas in the gas supply line; The pressure calculation unit, A pressure value measured by the pressure controller is used as the primary pressure of the flow resistance element, 4. The electrostatic chuck device according to claim 3, wherein a pressure of the thermally conductive gas in the gap is calculated using a flow rate value measured by the flow rate sensor as a flow rate value of the thermally conductive gas introduced into the gas supply line.

5. a pressure-type flow rate controller that measures and controls a flow rate of the thermally conductive gas flowing through the gas supply line; The pressure calculation unit, A pressure value measured by the pressure type flow rate controller is used as the primary pressure of the flow rate resistance element, 4. The electrostatic chuck device according to claim 3, wherein a pressure of the thermally conductive gas in the gap is calculated using a flow rate value measured by the pressure type flow rate controller as a flow rate value of the thermally conductive gas introduced into the gas supply line.

6. 6. The electrostatic chuck device according to claim 1, further comprising a diagnosis unit that compares the calculated pressure of the thermally conductive gas with a predetermined reference pressure to diagnose an abnormality in the pressure value of the thermally conductive gas applied to the attracted surface.

7. 7. The electrostatic chuck device according to claim 1, further comprising: a pressure of the thermally conductive gas in the gas supply line being adjusted so that the calculated pressure of the thermally conductive gas is within a predetermined range.

8. 7. The electrostatic chuck device according to claim 1, further comprising: a flow rate of the thermally conductive gas flowing through the gas supply line adjusted so that the calculated pressure of the thermally conductive gas is within a predetermined range.

9. 9. The electrostatic chuck device according to claim 1, further comprising a plurality of the gas supply lines, each of the gas supply lines being configured to supply the thermally conductive gas to a different region between the attracting surface and the attracted surface.

10. 10. The electrostatic chuck device according to claim 1, wherein the gas supply line is configured to be able to supply a plurality of types of the thermally conductive gases at an arbitrary mixing ratio.

11. a main leak line provided with a resistor and branching off from the gas supply line; a bypass line provided to bypass the resistor; an on-off valve provided on the bypass line; A valve control unit that controls the on-off valve, 11. The electrostatic chuck device according to claim 1, wherein a flow resistance of the bypass line is smaller than a flow resistance of the main leak line.

12. 1. A pressure calculation method for an electrostatic chuck device that attracts an object by electrostatic force, comprising: the electrostatic chuck device includes a suction plate having an suction surface for suctioning the object, and a gas supply line for supplying a thermally conductive gas to a gap between the suction surface and an attracted surface of the object, the gas supply line being provided with a flow resistance element that provides resistance when the thermally conductive gas flows; A pressure calculation method for calculating the pressure of the thermally conductive gas in the gap based on the primary side pressure of the flow resistance element, the flow rate of the thermally conductive gas passing through the flow resistance element, and the flow characteristics of the flow resistance element.

13. A pressure calculation program for an electrostatic chuck device that attracts an object by electrostatic force, the electrostatic chuck device includes a suction plate having an suction surface for suctioning the object, and a gas supply line for supplying a thermally conductive gas to a gap between the suction surface and an attracted surface of the object, the gas supply line being provided with a flow resistance element that provides resistance when the thermally conductive gas flows; A pressure calculation program for an electrostatic chuck device that causes a computer to function as a pressure calculation unit that calculates the pressure of the thermally conductive gas in the gap based on the primary side pressure of the flow resistance element, the mass flow rate of the thermally conductive gas passing through the flow resistance element, and the flow characteristics of the flow resistance element.

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