Electrostatic chuck device, pressure calculation method, and recording medium

Abstract

The present application provides an electrostatic chuck device, a pressure calculation method and a recording medium, the electrostatic chuck device adsorbs an object by electrostatic force, and has: an adsorption plate having an adsorption surface for adsorbing the object; a gas supply pipeline for supplying a heat-conducting gas to a gap between the adsorption surface and a surface to be adsorbed of the object; and a pressure calculation unit for calculating the pressure of the heat-conducting gas in the gap; a flow resistance element is arranged in the gas supply pipeline, and the flow resistance element becomes the resistance when the heat-conducting gas flows; and the pressure calculation unit calculates the pressure of the heat-conducting gas in the gap based on the pressure on one side of the flow resistance element, the flow of the heat-conducting gas passing through the flow resistance element, and the flow characteristic of the flow resistance element.

Description

Technical Field

[0001] This invention relates to an electrostatic clamp device that uses electrostatic force to attract objects, a pressure calculation method, and a recording medium. Background Technology

[0002] In the past, electrostatic chucks were used in semiconductor manufacturing processes employing plasma processing equipment such as plasma etching and plasma CVD systems to fix samples, such as silicon wafers, within a vacuum chamber. These electrostatic chucks consist of an adsorption plate that attracts the sample by electrostatic force and a metal base plate that contacts the back side of the adsorption plate. By using the electrostatic chuck, the back side (adsorbed surface) of the silicon wafer is adsorbed by the adsorption plate, thereby fixing the wafer. Furthermore, the plasma heat acting on the silicon wafer is released towards the base plate for cooling, thus achieving uniform surface temperature distribution.

[0003] However, there are minute irregularities on the adsorption surface of the adsorption plate or the adsorbed surface of the silicon wafer. Therefore, even when the silicon wafer is adsorbed by an electrostatic clamping device, a tiny gap of about 10 μm in thickness is generated between the adsorbed surface and the adsorption surface, resulting in a smaller physical contact area and reduced heat conduction efficiency. Conventionally, multiple gas supply ports are provided on the adsorption surface of the adsorption plate, and thermally conductive gas is supplied to the gap between the adsorbed surface of the silicon wafer and the adsorption surface of the adsorption plate, thereby effectively releasing the plasma heat on the silicon wafer to the adsorption plate side (Patent Document 1).

[0004] Existing technical documents

[0005] Patent Document 1: Japanese Patent Publication No. 2020-053576

[0006] In semiconductor manufacturing processes using the aforementioned plasma processing apparatus, improving the uniformity of the wafer's surface temperature is crucial for achieving high dimensional accuracy in the processing of objects such as wafers. Furthermore, this surface temperature uniformity is highly dependent on the pressure of the thermally conductive gas acting on the adsorbed surface of the wafer (hereinafter also referred to as wafer back pressure). Therefore, controlling the wafer back pressure is key to improving the accuracy of wafer processing dimensions. Additionally, from the perspective of identifying anomalies or signs such as decreased stability of the electrostatic chuck's adsorption force due to years of degradation, controlling the wafer back pressure is paramount in semiconductor manufacturing processes. However, conventionally, there has been no technology for controlling the wafer back pressure when adsorbing objects using an electrostatic chuck. Summary of the Invention

[0007] The present invention was made to solve the above-mentioned problems, and its main objective is to control the pressure on the back side of the wafer in the semiconductor manufacturing process using an electrostatic chuck device.

[0008] That is, the electrostatic chuck device of the present invention adsorbs an object by electrostatic force, characterized by comprising: an adsorption plate having an adsorption surface for adsorbing the object; a gas supply pipe for supplying a thermally conductive gas to the gap between the adsorption surface and the adsorbed surface of the object; and a pressure calculation unit for calculating the pressure of the thermally conductive gas in the gap, wherein a flow resistance element is provided in the gas supply pipe, the flow resistance element acting as a 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.

[0009] According to such an electrostatic chuck device, by utilizing the flow characteristics of the flow resistance element provided in the gas supply pipe, that is, the inherent characteristics that represent the relationship between the primary side pressure (e.g., the pressure in the gas supply pipe) and the secondary side pressure (e.g., the pressure on the back side of the wafer) of the flow resistance element and the flow rate of the thermally conductive gas passing through, the pressure on the back side of the wafer can be calculated and controlled.

[0010] Specific embodiments of the electrostatic chuck device include: the air supply pipe having an air supply channel formed in the adsorption plate with an opening on the adsorption surface, and the flow resistance element being disposed in the air supply channel.

[0011] With this electrostatic chuck device, flow resistance elements are placed in the air supply channel at the opening of the adsorption surface of the adsorption plate, thus enabling more accurate calculation of the pressure on the back side of the wafer.

[0012] The "flow resistance element" can be any element as long as it has the flow characteristics that determine the flow rate of the thermally conductive gas passing through by the pressure on the primary side and the pressure on the secondary side, but it is particularly preferred to be a laminar flow element resistance body.

[0013] Laminar flow element resistance bodies possess excellent machining accuracy and reproducibility. Therefore, by employing laminar flow element resistance bodies as flow resistance elements, the pressure of thermally conductive gas in the gap between the adsorption surface and the adsorbed surface can be calculated with higher accuracy. In addition, the design freedom of laminar flow element resistance bodies is high, thus increasing the degree of freedom in the outer diameter of the thermally conductive gas outlet, which is expected to suppress the occurrence of arc discharge.

[0014] A specific configuration of the pressure calculation unit can be described as follows: the flow rate of the thermally conductive gas passing through the flow resistance element is calculated based on the relationship between the flow rate of the thermally conductive gas introduced into the gas supply pipe and the material balance representing the flow rate of the thermally conductive gas in the gas supply pipe.

[0015] Specific examples of electrostatic clamp devices include: a pressure controller equipped with a flow sensor that measures and controls the pressure of the thermally conductive gas in the gas supply pipe; a pressure calculation unit that uses the pressure value measured by the pressure controller as the primary pressure of the flow resistance element and the flow value measured by the flow sensor as the flow rate of the thermally conductive gas introduced into the gas supply pipe, and calculates the pressure of the thermally conductive gas in the gap.

[0016] Other specific embodiments of the electrostatic clamp device include: a pressure flow controller that measures and controls the flow rate of the thermally conductive gas flowing in the gas supply pipe; a pressure calculation unit that uses the pressure value measured by the pressure flow controller as the primary pressure of the flow resistance element and the flow rate value measured by the pressure flow controller as the flow rate of the thermally conductive gas introduced into the gas supply pipe, and calculates the pressure of the thermally conductive gas in the gap.

[0017] In order to diagnose any abnormalities on the back side of the wafer during plasma processing, such as a decrease in the adsorption force on the wafer due to years of device deterioration, the electrostatic chuck device preferably also includes a diagnostic unit that compares the calculated pressure of the thermally conductive gas with a predetermined reference pressure to diagnose any abnormalities in the pressure value of the thermally conductive gas on the adsorbed surface.

[0018] Preferably, the electrostatic clamp device is configured to adjust the pressure of the thermally conductive gas in the gas supply pipe so that the calculated pressure of the thermally conductive gas is within a specified range.

[0019] Preferably, the electrostatic clamp device is configured to adjust the flow rate of the thermally conductive gas flowing in the gas supply pipe so that the calculated pressure of the thermally conductive gas is within a specified range.

[0020] Preferably, the electrostatic clamp device is configured to have a plurality of gas supply pipes, each gas supply pipe supplying the thermally conductive gas to different regions between the adsorption surface and the adsorbed surface.

[0021] With this electrostatic chuck device, the pressure on the back of the wafer can be adjusted according to each region.

[0022] A specific embodiment of the electrostatic clamp device can be configured such that the gas supply pipe can supply various thermally conductive gases in any mixing ratio.

[0023] According to such an electrostatic chuck device, by making the thermally conductive gas a mixture of multiple gases, the amount of expensive gases (such as helium) used can be reduced, thereby reducing costs.

[0024] Furthermore, preferably, the electrostatic clamp device is configured to calculate the flow rate Q of the thermally conductive gas discharged from the gap based on the time-varying pressure of the thermally conductive gas in the gas supply pipe. LEAK In this case, preferably, the electrostatic clamp device calculates the flow rate Q based on the following formula (a). LEAK .

[0025]

[0026] Here,

[0027] V: The volume of the flow channel that constitutes the gas supply pipeline;

[0028] Z: Compressibility coefficient of thermally conductive gases;

[0029] R u The gas constant of a thermally conductive gas;

[0030] T gas The temperature of the thermally conductive gas flowing in the gas supply pipeline;

[0031] dP / dT: The time-varying pressure of the thermally conductive gas in the gas supply pipeline.

[0032] If configured in this way, it is possible to control the flow rate of thermally conductive gas discharged from the gap between the gas and the object being adsorbed, and to monitor the deterioration of the electrostatic chuck device, etc.

[0033] However, in the aforementioned electrostatic chuck device, if the pressure of the thermally conductive gas supplied to the back of the wafer is too high, the wafer may detach from the adsorption surface. Therefore, existing electrostatic chuck devices are configured with an exhaust pipe branching from the gas supply pipe and equipped with a resistance element to discharge excess thermally conductive gas at a predetermined flow rate. On the other hand, this exhaust pipe is also used to discharge thermally conductive gas remaining in the gas supply pipe after plasma processing. Because a resistance element is provided in the exhaust pipe, there is a problem that the thermally conductive gas cannot be discharged immediately after plasma processing, resulting in a delay. Consequently, when plasma processing ends and the electrostatic chuck device switches to the non-clamping state, the thermally conductive gas remaining in the gas supply pipe flows into the vacuum chamber, potentially generating sparks and causing machine malfunction.

[0034] Therefore, preferably, the electrostatic chuck device includes: a main exhaust pipe branching from the air supply pipe and provided with a resistance body; a bypass pipe provided to bypass the resistance body; a switching valve provided on the bypass pipe; and a valve control unit for controlling the switching valve, wherein the electrostatic chuck device is configured such that the flow resistance of the bypass pipe is less than the flow resistance of the main exhaust pipe.

[0035] With this configuration, when plasma treatment ends and the electrostatic chuck switches to the non-clamping state, the thermally conductive gas can be immediately discharged through a bypass pipe with relatively low flow resistance by opening the switching valve. This reduces the risk of sparks generated by the thermally conductive gas flowing into the vacuum chamber immediately after plasma treatment.

[0036] Furthermore, the pressure calculation method of the present invention is a pressure calculation method in an electrostatic chuck device that adsorbs an object by electrostatic force. The electrostatic chuck device comprises: an adsorption plate having an adsorption surface for adsorbing the object; and a gas supply pipe supplying a thermally conductive gas to the gap between the adsorption surface and the adsorbed surface of the object. A flow resistance element is provided in the gas supply pipe, which acts as a resistance to the flow of the thermally conductive gas. The pressure of the thermally conductive gas in the gap is calculated based on the primary 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.

[0037] Furthermore, the recording medium of the present invention records a pressure calculation program for an electrostatic chuck device that uses electrostatic force to adsorb an object. The electrostatic chuck device includes: an adsorption plate having an adsorption surface for adsorbing the object; and a gas supply pipe supplying a thermally conductive gas to the gap between the adsorption surface and the adsorbed surface of the object. A flow resistance element is provided in the gas supply pipe, which acts as a resistance to the flow of the thermally conductive gas. The pressure calculation program enables a computer to function as a pressure calculation unit, which 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.

[0038] Based on this pressure calculation method and procedure, the same effect as the electrostatic chuck device of the present invention described above can be obtained.

[0039] According to the present invention configured in this way, it is possible to control the pressure on the back side of the wafer in a semiconductor manufacturing process using an electrostatic chuck device. Attached Figure Description

[0040] Figure 1This is a schematic diagram showing the overall structure of the electrostatic chuck device according to this embodiment.

[0041] Figure 2 This is a schematic cross-sectional view showing the configuration of an electrostatic chuck device according to the same embodiment.

[0042] Figure 3 This is a perspective view schematically showing the configuration of the electrostatic clamp head and cooling section of the same embodiment.

[0043] Figure 4 This is a perspective view schematically showing the configuration of the electrostatic clamp head and cooling section of the same embodiment.

[0044] Figure 5 This is a diagram schematically showing the configuration of the air supply unit in the same embodiment.

[0045] Figure 6 This is a schematic diagram illustrating the configuration of the air supply unit in other embodiments.

[0046] Figure 7 This is a schematic diagram illustrating the configuration of the air supply unit in other embodiments.

[0047] Figure 8 This is a schematic diagram illustrating the configuration of the air supply unit in other embodiments.

[0048] Figure 9 This is a schematic diagram illustrating the configuration of the air supply unit in other embodiments.

[0049] Figure 10 This is a schematic diagram illustrating the configuration of the air supply unit in other embodiments.

[0050] Explanation of reference numerals in the attached figures

[0051] 100…Electrostatic chuck device

[0052] 111…Adsorption surface

[0053] 31…Gas supply pipeline

[0054] 31a…Gas supply port

[0055] 34… Flow resistance element

[0056] W…chip (object)

[0057] S…the surface being adsorbed

[0058] G…gap Detailed Implementation

[0059] Hereinafter, an embodiment of the electrostatic chuck device 100 according to the present invention will be described with reference to the accompanying drawings.

[0060] like Figure 1 As shown, the electrostatic chuck device 100 of this embodiment is used, for example, in the vacuum chamber C of a semiconductor manufacturing apparatus using plasma, to electrostatically adsorb a wafer W that is to be processed. Specifically, as Figure 2 As shown, the electrostatic chuck device 100 includes: an electrostatic chuck head 1 having an adsorption surface 111 for electrostatically adsorbing the wafer W; a cooling section 2 having a cooling surface 211 for cooling the electrostatic chuck head 1; and a gas supply section 3 supplying a thermally conductive gas (also called a back-side gas) to the gap G between the adsorption surface 111 of the electrostatic chuck head 1 and the adsorbed surface S of the wafer W. Furthermore, the vacuum chamber C is configured to be evacuated by a vacuum pump V1.

[0061] like Figure 2 as well as Figure 3 As shown, the electrostatic clamp head 1 includes: an adsorption plate 11, formed of an insulator such as ceramic or glass, and in the shape of a circular flat plate; an internal electrode 12 embedded in the adsorption plate 11; and a power supply 13 that applies voltage to the internal electrode 12. By applying voltage to the internal electrode 12 using the power supply 13, a dielectric polarization phenomenon is generated within the adsorption plate 11, and the upper surface 111 of the adsorption plate 11 becomes a generally planar adsorption surface. The electrostatic clamp head 1 of this embodiment is bipolar, but it is not limited to this and can also be unipolar.

[0062] like Figures 2-4 As shown, the cooling section 2 includes: a metal base plate 21, which is circular and flat; a refrigerant flow channel 212 formed within the base plate 21; and a refrigerant flow mechanism (not shown) such as a refrigerator, through which refrigerant flows in the refrigerant flow channel 212. By utilizing the refrigerant flow mechanism to allow refrigerant to flow in the refrigerant flow channel 212, the overall temperature of the base plate 21 decreases, and the upper surface 211 of the base plate 21 becomes a generally planar cooling surface. The adsorption plate 11 is placed on the base plate 21 such that its lower surface 112 (back side) contacts the cooling surface 211 of the base plate 21. The refrigerant flow channel 212 is formed inside the base plate 21 in a direction parallel to the cooling surface 211.

[0063] like Figure 5 As shown, the gas supply unit 3 includes: a gas supply pipe 31, equipped with a flow controller 32 for controlling the flow rate of the thermally conductive gas; a control device 33 for controlling the flow controller 32, etc.; and an exhaust pipe L, which branches off from the gas supply pipe 31. The thermally conductive gas can be, for example, helium, argon, or any gas mixture formed by mixing multiple gases in any ratio.

[0064] The gas supply pipe 31 is connected to a gas supply source (not shown) on the upstream side, and supplies thermally conductive gas from the gas supply port 31a located at the downstream end to the gap G between the adsorption surface 111 and the adsorbed surface S of the wafer W. The gas supply port 31a is formed on the adsorption surface 111 of the adsorption plate 11.

[0065] Specifically, the gas supply pipe 31 comprises, from the downstream side, the following components in sequence: a first internal flow channel (the gas supply channel described in the claims) 311, formed within the adsorption plate 11; a second internal flow channel 312, formed within the base plate 21 in communication with the first internal flow channel 311; and a piping flow channel (not shown), communicating with the second internal flow channel 312, and formed by piping connecting the base plate 21 to the gas supply source.

[0066] like Figure 2 as well as Figure 4 As shown, multiple first internal flow channels 311 extend through the adsorption plate 11 along its thickness direction and are formed with openings on the adsorption surface 111. Each opening of the first internal flow channel 311 on the adsorption surface 111 serves as an air supply port 31a. Each air supply port 31a is formed in a rotationally symmetrical manner, for example, about the rotation axis of the adsorption plate 11. In this embodiment, each first internal flow channel 311 is formed in multiple concentric rows (here, two rows) on the outer periphery of the adsorption plate 11, with each row arranged at approximately equal intervals along the circumferential direction.

[0067] Specifically, each of the first internal flow channels 311 is composed of a straight through hole 113 with a circular cross-section that extends through the adsorption plate 11 along the thickness direction. The diameter (inner diameter) of the through hole 113 is about a few μm to tens of μm (e.g., 0.03 mm), and the length (dimension along the axial direction) is about a few mm (e.g., 2 mm), but these dimensions can be appropriately changed.

[0068] The second internal flow channel 312 is formed to extend through the base plate 21 along the thickness direction, with its upstream end opening on the lower surface of the base plate 21 and its downstream end opening on the upper surface (cooling surface) 211 of the base plate 21, thereby communicating with the first internal flow channel 311.

[0069] like Figure 2 as well as Figure 3 As shown, a groove 213 is formed along the in-plane direction on the upper surface 211 of the base plate 21. At least a portion of the groove 213 penetrates the base plate 21 along its thickness direction and opens on its lower surface. By placing the adsorption plate 11 to cover the groove 213, a second internal flow channel 312 is formed by the inner surface of the groove 213 and the lower surface 112 of the adsorption plate 11. The groove 213 is formed such that it passes directly below each through hole 113 of the adsorption plate 11 when the adsorption plate 11 is placed on the base plate 21.

[0070] A flow controller 32 measures and controls the flow rate of the passing gas and is installed in the piping flow path. Specifically, this flow controller 32 may be a pressure-type mass flow controller, which includes: a pressure sensor to measure the pressure of the passing gas, a flow sensor to measure the gas flow rate, a fluid control valve, and a valve controller to control the opening degree of the fluid control valve. The flow controller 32 provides feedback control of the fluid control valve opening degree, etc., to ensure that the measured gas flow rate matches the target value set by the control device 33.

[0071] The control device 33 is a general-purpose or even special-purpose computer with a built-in CPU and internal memory. This control device 33 coordinates the operation of the CPU and its peripheral devices based on a predefined program stored in the internal memory, thereby achieving... Figure 5 As shown, at least the flow target setting unit 334 functions as the flow target value set by the flow controller 32.

[0072] The exhaust pipe L branches off from the downstream portion of the gas supply pipe 31 from the flow controller 32. The exhaust pipe L is configured such that exhaust is achieved by the vacuum pump V2 through an arbitrary resistance body R (e.g., a throttle orifice) through which a certain flow rate of gas passes.

[0073] Furthermore, the electrostatic clamp device 100 of this embodiment is provided with flow resistance elements 34 in each of the first internal flow channels 311 of the air supply pipe 31.

[0074] The flow resistance element 34 acts as a resistance to the flow of thermally conductive gas, and has an inherent flow characteristic where the mass flow rate of the gas passing through it is determined based on the primary side pressure, the secondary side pressure, and the gas temperature. In this embodiment, it is a laminar flow element resistance body. Here, the flow rate of the thermally conductive gas passing through the laminar flow element resistance body 34 is determined based on the pressure of the thermally conductive gas in the gas supply pipe 31 (primary side pressure), the pressure of the thermally conductive gas in the gap G between the adsorption surface 111 and the adsorbed surface S (secondary side pressure, hereinafter also referred to as the wafer back side pressure), and the temperature of the thermally conductive gas passing through it.

[0075] Specifically, the laminar flow element resistance body 34 is composed of a flow channel forming member 341 having a flow channel (hereinafter also referred to as a resistance flow channel) 341a that serves as resistance. This flow channel forming member 341 is cylindrical, and its diameter (outer diameter) and length (axial dimension) are approximately the same as the diameter (inner diameter) and length of the through hole 113 of the adsorption plate 11. Figure 4As shown, each flow channel forming member 341 is fitted into each through hole 113 of the adsorption plate 11 with a tight fit tolerance. The flow channel forming member 341 can be made of any insulating material, such as ceramic. Preferably, the downstream end face of the laminar flow element resistance body 34 is configured to be on the same plane as the adsorption surface 111 of the adsorption plate 11.

[0076] One or more resistance channels 341a are formed along the axial direction of the channel forming member 341. Each resistance channel 341a is formed by passing through the channel forming member 341 along the axial direction and is a straight channel with a circular cross-section. For example, multiple resistance channels 341a can be formed on the axis of the channel forming member 341 or arranged regularly around the axis.

[0077] Furthermore, the electrostatic chuck device 100 of this embodiment is characterized in that the control device 33 further functions as a pressure calculation unit 331, a storage unit 332, and a diagnostic unit 333.

[0078] Furthermore, in the electrostatic chuck device 100 of this embodiment, the pressure calculation unit 331 is configured to calculate the pressure based on the mass flow rate Q of the thermally conductive gas supplied from the air supply port 31a. ESC Calculate the primary side pressure P1 of the laminar flow element resistance body 34, the inherent flow characteristics of the laminar flow element resistance body 34, and the back-side pressure P of the wafer. wafer Additionally, mass flow rate Q ESC In this embodiment, where the laminar flow element resistance body 34 is disposed in the through hole 113, the mass flow rate of the thermally conductive gas passing through the first internal flow channel 311 (through hole 113) formed in the adsorption plate 11 is the mass flow rate of the thermally conductive gas passing through the laminar flow element resistance body 34.

[0079] Specifically, the pressure calculation unit 331 is configured to: calculate the mass flow rate of the thermally conductive gas flowing in the gas supply pipe 31 based on the following relationship (1) (i.e., the balance between the amount of thermally conductive gas entering the gas supply pipe 31 and the amount of thermally conductive gas exiting the gas supply pipe 31), and the mass flow rate Q of the thermally conductive gas introduced into the gas supply pipe 31. in Calculate the mass flow rate Q of the thermally conductive gas supplied from gas outlet 31a. ESC Furthermore, the pressure calculation unit 331 is configured to calculate the mass flow rate Q of the thermally conductive gas. ESC The wafer back pressure P is calculated using the following equation (2), which represents the relationship between the inherent flow characteristics of the laminar flow element resistance body 34 and the laminar flow characteristics. wafer .

[0080] [Number 1]

[0081]

[0082] In equation (1),

[0083] Q in : The mass flow rate of the thermally conductive gas introduced into the gas supply pipeline 31;

[0084] Q VAC The mass flow rate of the thermally conductive gas discharged from the exhaust pipe L is also the mass flow rate passing through the resistance body R.

[0085] (V / Z·R u ·T gas (dP / dT): Mass flow rate Q of the thermally conductive gas discharged from between the adsorption plate 11 and the wafer W into the chamber. LEAK ;

[0086] V: The volume of the flow path from the flow controller 32 in the gas supply pipe 31 to the laminar flow element resistance body 34;

[0087] Z: The compressibility of the gas (in this case, Z = 1);

[0088] R u Gas constant (8.3145 J·mol⁻¹) 1 ·K- 1 );

[0089] T gas The average temperature of the heat-conducting gas in the flow channel from the flow controller 32 in the gas supply pipe 31 to the laminar flow element resistance body 34;

[0090] dP / dt: The time-varying pressure of the thermally conductive gas in the flow channel from the flow controller 32 in the gas supply pipe 31 to the laminar flow element resistance body 34.

[0091] Furthermore, considering that the surface properties (e.g., shape, roughness, etc.) of the adsorption surface 111 of the adsorption plate 11 are not uniform in the plane, and that the heat energy exchange during the process is unstable, the mass flow rate Q will be significantly reduced after a sufficient period of time since the thermally conductive gas is supplied through the gas supply pipe 31. LEAK It is also possible that it has not yet reached a steady state (stationary state), and dP / dt has not yet become 0.

[0092] Here, the pressure calculation unit 331 obtains the mass flow rate Q from the flow controller 32. in The average temperature T is obtained from the thermometer T1 installed in the gas supply pipeline 31. gas The mass flow rate Q of the discharged gas is obtained from the storage unit 332. VAC The volume V of the flow channel, the compressibility Z, and the gas constant R uBased on the above information and equation (1), the mass flow rate Q of the thermally conductive gas supplied from the gas supply port 31a is calculated. ESC .

[0093] [Number 2]

[0094] Q ESC =f res (P1, P) wafer T ESC (2)

[0095] In equation (2),

[0096] f res : A function representing the flow characteristics of the laminar flow element resistance body 34;

[0097] P1: Pressure on the primary side (upstream side) of the laminar flow element resistance body 34;

[0098] P wafer : Backside pressure of the wafer (the pressure on the secondary side of the laminar flow element resistance body 34);

[0099] T ESC The temperature of the thermally conductive gas passing through the laminar flow element resistance body 34 (here, it is considered to be equal to the temperature of the adsorption plate 11).

[0100] The pressure calculation unit 331 is configured to obtain the primary side pressure P1 from the pressure measured by the flow controller 32, and obtain the temperature T of the thermally conductive gas from the fiber optic thermometer T2 that measures the temperature of the adsorption plate 11. ESC The flow characteristic function f is obtained from the storage unit 332. res Based on this information and Equation (2), the pressure P on the back of the wafer is calculated. wafer The flow characteristic function f is pre-stored in storage unit 332. res For example, the pressure P1 on the primary side of the laminar flow element resistance body 34 and the pressure P on the secondary side of the laminar flow element resistance body 34. wafer The temperature T of the thermally conductive gas passing through the laminar flow element resistance body 34 ESC The graph is a function of the mass flow rate passing through the laminar flow element resistance body 34 as the output variable, with the input variable being the input variable.

[0101] The diagnostic unit 333 diagnoses whether there are any abnormalities on the adsorption surface S of the wafer W. Specifically, the diagnostic unit 333 is configured to: calculate the back surface pressure P of the wafer calculated by the pressure calculation unit 331. wafer and the specified pressure P pre-stored in storage unit 332 s By comparison, an abnormality can be diagnosed on the adsorption surface S of wafer W. For example, the pressure P on the back side of the wafer. wafer With pressure Ps If the absolute value of the difference exceeds a specified value, an abnormality is diagnosed at the adsorption surface S of the wafer W; if it is below the specified value, it is diagnosed as normal. Additionally, the pressure P... s It is appropriately set according to the content of the vacuum treatment of wafer W.

[0102] Furthermore, the aforementioned flow target setting unit 334 is configured such that the wafer back pressure P calculated by the pressure calculation unit 331 is... wafer The flow target value is set to a value within a specified range for the flow controller 32 and then sent to the flow controller 32. Specifically, the flow target setting unit 334 is configured to: calculate the wafer back pressure P from the pressure calculation unit 331. wafer The target value P pre-stored in storage unit 332 t The comparison is made in a way that the absolute value of the difference is used to determine the flow target value based on the prescribed relationship calculated in advance through experimentation or simulation.

[0103] According to the electrostatic chuck device 100 of this embodiment, a first internal flow channel 311 with a pre-known flow characteristic f is provided in the air supply port 31a of the air supply pipe 31. res The flow resistance element 34 enables the utilization of this flow characteristic f res And the primary side pressure P1 of the flow resistance element 34 controls the back side pressure P of the wafer. wafer This helps improve the dimensional accuracy of the wafer W and allows for the detection of anomalies or signs such as decreased adhesion stability due to years of degradation. Furthermore, the flow resistance element 34, which acts as a barrier to the flow of thermally conductive gas, is positioned in the first internal flow channel 311 to block the gas supply port 31a. Therefore, it is possible to suppress the outflow of excess thermally conductive gas from the gas supply port 31a when the wafer W is not clamped or during cleaning of the processing chamber.

[0104] Furthermore, the present invention is not limited to the embodiments described herein.

[0105] For example, such as Figure 6 As shown, the electrostatic chuck device 100 in other embodiments can be configured to include a plurality of gas supply pipes 31, each gas supply pipe 31 supplying a thermally conductive gas to different regions between the adsorption surface 111 of the adsorption plate 11 and the adsorbed surface S of the wafer W. In this case, the adsorption surface 111 of the adsorption plate 11 can be divided into a plurality of gas supply regions corresponding to the number of gas supply pipes 31, and each gas supply pipe 31 can supply a thermally conductive gas 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 pipe 31 can be set according to each gas supply pipe 31.

[0106] In addition, such as Figure 7 As shown, in other embodiments of the electrostatic chuck device 100, the air supply unit 3 may not have an exhaust pipe L. In this case, the pressure calculation unit 331 is configured such that, in the above formula (1), "Q" is used as the pressure calculation unit. VAC =0” calculate P wafer .

[0107] Furthermore, the electrostatic chuck device 100 of the above embodiment includes a pressure-type flow controller 32, but is not limited thereto. The electrostatic chuck device 100 of the present invention is configured to be able to measure the mass flow rate Q of the thermally conductive gas introduced into the gas supply pipe 31. in The pressure P1 of the thermally conductive gas in the gas supply pipe 31 can be used to control the pressure P on the back of the wafer. wafer .

[0108] For example, such as Figure 8 As shown, in other embodiments, the electrostatic clamp device 100 can replace the flow controller 32 with a pressure controller 35 that measures and controls the pressure of the thermally conductive gas in the gas supply pipe 31. Specifically, the pressure controller 35 can include, for example, a valve controller that includes a flow sensor, a fluid control valve, a pressure sensor, and provides feedback control of the opening of the fluid control valve based on the output of the pressure sensor. According to this embodiment, the pressure calculation unit 331 can also use the pressure value measured by the pressure controller 35 as the primary side pressure P1 of the flow resistance element 34, and use the flow rate value measured by the flow sensor included in the pressure controller 35 as the flow rate Q of the thermally conductive gas introduced into the gas supply pipe 31. in Calculate the pressure P on the back of the chip wafer .

[0109] In addition, and not limited to this, such as Figure 9 As shown, it can replace the flow controller 32 and have the function of controlling the mass flow rate Q of the thermally conductive gas introduced into the gas supply pipe 31. in The flow meter 36 is used for measuring mass flow and the pressure meter 37 is used to measure the pressure P1 of the thermally conductive gas in the gas supply pipeline 31.

[0110] Furthermore, in the described embodiment, it is not limited to providing flow resistance elements 34 in all of the plurality of first internal flow channels 311. In other embodiments, flow resistance elements 34 may be provided only in a portion of the plurality of first internal flow channels 311.

[0111] Furthermore, although the flow resistance element 34 is disposed within the first internal flow channel 311 in the described embodiment, it is not limited thereto. In other embodiments, the flow resistance element 34 may be formed within the flow channel of the gas supply pipe 31 that communicates with the gap G, such as the second internal flow channel 312 or a piping flow channel (not shown) connecting the base plate 21 to the gas supply source. Additionally, to more accurately calculate the pressure on the back side of the wafer, it is preferable that the flow resistance element 34 is disposed further downstream in the gas supply pipe 31.

[0112] Furthermore, the flow resistance element 34 in the described embodiment is a laminar flow element resistance body, but it is not limited to this. As long as it has the flow characteristics that determine the flow rate of the thermally conductive gas passing through it by the pressure on the primary side and the pressure on the secondary side, the flow resistance element 34 can be of any type.

[0113] Furthermore, the flow resistance element 34 may not be a resistance body disposed within the flow channel of the gas supply pipe 31. The flow resistance element 34 may be, for example, the flow channel itself of the gas supply pipe 31 (such as the first internal flow channel 311), whose flow characteristics are known. With such a configuration, the pressure on the back side of the wafer can also be controlled by utilizing the flow characteristics of the flow channel.

[0114] Additionally, the electrostatic chuck device 100 in other embodiments includes a resistance changing mechanism 4, which changes the magnitude of the flow resistance of the exhaust pipe L relative to the thermally conductive gas. Specifically, as Figure 10As shown, the resistance changing mechanism 4 includes: a bypass pipe 41 installed in the exhaust pipe L to bypass the resistance body R; a switching valve 42 installed on the bypass pipe 41; and a valve control unit 335 for controlling the switching valve 42. In this embodiment, the bypass pipe 41 is configured to branch upstream of the resistance body R and merge downstream of the resistance body R in the exhaust pipe L. When the switching valve 42 is open, the flow resistance (pipeline resistance) of the bypass pipe 41 is set to be smaller than the flow resistance of the main exhaust pipe 43 on which the resistance body R is installed. The switching valve 42 is configured to switch open and closed according to a control signal from the valve control unit 335, and is, for example, a pneumatic valve, a piezoelectric actuated valve, a solenoid actuated valve, a thermal actuated valve, etc. The switching valve 42 is normally closed. The valve control unit 335 functions via the control device 33, sending a control signal to the switching valve 42 to switch its open and closed state. In this embodiment, the valve control unit 335 is configured such that if a signal indicating an intention to release (non-clamping) the electrostatic chuck head 1 from the wafer is received, a signal is immediately sent to the valve control unit 335 to open the valve control unit 335. Other embodiments of the electrostatic chuck device 100, due to the presence of such a resistance changing mechanism 4, can immediately discharge thermally conductive gas via the bypass pipe 41 when the electrostatic chuck head 1 switches to a non-clamping state. This reduces the risk of sparks generated due to thermally conductive gas flowing into the vacuum chamber C immediately after plasma processing.

[0115] Furthermore, when the electrostatic chuck device 100 is equipped with the resistance changing mechanism 4, the bypass pipe 41 can be configured such that it does not merge downstream of the resistance body R and exhausts gas via another vacuum pump. Additionally, the bypass pipe 41 may not be configured to branch upstream of the resistance body R in the exhaust pipe L. For example, the bypass pipe 41 may be configured to branch upstream or downstream of the bifurcation point of the exhaust pipe L in the gas supply pipe 31. Furthermore, any resistance body, such as a flow resistance element, can be provided in the bypass pipe 41. In such cases, as long as the flow resistance of the bypass pipe 41 is set to be less than the flow resistance of the main exhaust pipe 43, the thermally conductive gas can be immediately discharged via the bypass pipe 41 when the electrostatic chuck head 1 switches to the non-clamping state.

[0116] Furthermore, the present invention is not limited to the described embodiments, and various modifications can be made without departing from its spirit.

[0117] Industrial availability

[0118] The electrostatic chuck device according to the present invention can control the pressure on the back side of the wafer in a semiconductor manufacturing process using an electrostatic chuck device.

Claims

1. An electrostatic chuck device that adsorbs an object by electrostatic force, characterized in that, The electrostatic chuck device includes: An adsorption plate has an adsorption surface that adsorbs the object. A gas supply pipe supplies a thermally conductive gas to the gap between the adsorption surface and the adsorbed surface of the object; and The pressure calculation unit calculates the pressure of the thermally conductive gas in the gap. The gas supply pipe includes a gas supply channel formed within the adsorption plate with an opening on the adsorption surface. A flow resistance element is provided in the gas supply channel, which acts as a resistance to the flow of the thermally conductive gas. 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. The primary side pressure of the flow resistance element is the pressure on the upstream side of the flow resistance element.

2. The electrostatic chuck device according to claim 1, characterized in that, The pressure calculation unit calculates the flow rate of the thermally conductive gas passing through the flow resistance element based on the relationship between the flow rate of the thermally conductive gas introduced into the gas supply pipe and the material balance representing the flow rate of the thermally conductive gas in the gas supply pipe.

3. The electrostatic chuck device according to claim 2, characterized in that, It also includes a pressure controller equipped with a flow sensor to measure and control the pressure of the thermally conductive gas within the gas supply pipeline. The pressure calculation unit is configured as follows: The pressure value measured by the pressure controller is used as the primary pressure of the flow resistance element, and the flow value measured by the flow sensor is used as the flow rate of the thermally conductive gas introduced into the gas supply pipe. The pressure of the thermally conductive gas in the gap is then calculated.

4. The electrostatic chuck device according to claim 2, characterized in that, It also includes a pressure flow controller that measures and controls the flow rate of the thermally conductive gas flowing in the gas supply pipeline. The pressure calculation unit is configured as follows: The pressure value measured by the pressure flow controller is used as the primary pressure of the flow resistance element, and the flow rate value measured by the pressure flow controller is used as the flow rate value of the thermally conductive gas introduced into the gas supply pipeline. The pressure of the thermally conductive gas in the gap is then calculated.

5. The electrostatic chuck device according to any one of claims 1 to 4, characterized in that, It also includes a diagnostic unit that compares the calculated pressure of the thermally conductive gas with a specified reference pressure to diagnose any abnormalities in the pressure value of the thermally conductive gas on the adsorbed surface.

6. The electrostatic chuck device according to any one of claims 1 to 4, characterized in that, The pressure of the thermally conductive gas in the gas supply pipeline is adjusted so that the calculated pressure of the thermally conductive gas is within a specified range.

7. The electrostatic chuck device according to any one of claims 1 to 4, characterized in that, The flow rate of the thermally conductive gas flowing in the gas supply pipe is adjusted so that the calculated pressure of the thermally conductive gas is within a specified range.

8. The electrostatic chuck device according to any one of claims 1 to 4, characterized in that, The configuration includes multiple gas supply pipes, each supplying the thermally conductive gas to different regions between the adsorption surface and the adsorbed surface.

9. The electrostatic chuck device according to any one of claims 1 to 4, characterized in that, The gas supply pipeline is configured to supply various thermally conductive gases in any mixing ratio.

10. The electrostatic chuck device according to any one of claims 1 to 4, characterized in that, have: The main exhaust pipe branches off from the gas supply pipe and is equipped with a resistance body; A bypass pipe is provided to bypass the resistance body; A switching valve is provided on the bypass pipe; and The valve control unit controls the on / off valve. The electrostatic clamp device is configured such that the flow resistance of the bypass pipe is less than the flow resistance of the main exhaust pipe.

11. A pressure calculation method, which is a pressure calculation method in an electrostatic clamp device that uses electrostatic force to adsorb an object, characterized in that... The electrostatic chuck device includes: an adsorption plate having an adsorption surface for adsorbing the object; and a gas supply pipe for supplying a thermally conductive gas into the gap between the adsorption surface and the adsorbed surface of the object. The gas supply pipe has a gas supply channel formed within the adsorption plate with an opening on the adsorption surface, and a flow resistance element is provided in the gas supply channel to resist the flow of the thermally conductive gas. In the pressure calculation method, the pressure of the thermally conductive gas in the gap is calculated 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. The primary side pressure of the flow resistance element is the pressure on the upstream side of the flow resistance element.

12. A recording medium recording a pressure calculation program, said pressure calculation program being a pressure calculation program for an electrostatic clamp device that uses electrostatic force to attract an object, characterized in that, The electrostatic chuck device includes: an adsorption plate having an adsorption surface for adsorbing the object; and a gas supply pipe for supplying a thermally conductive gas into the gap between the adsorption surface and the adsorbed surface of the object. The gas supply pipe has a gas supply channel formed within the adsorption plate with an opening on the adsorption surface, and a flow resistance element is provided in the gas supply channel to resist the flow of the thermally conductive gas. The pressure calculation program enables the computer to function as a pressure calculation unit, which 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. The primary side pressure of the flow resistance element is the pressure on the upstream side of the flow resistance element.

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