Thermal correction wafer bearing table, photoetching equipment and high-order overlay error correction method

Abstract

The invention provides a thermal correction wafer bearing table, photoetching equipment and a high-order overlay error correction method, and the thermal correction wafer bearing table sequentially comprises a vacuum chuck which comprises an array composed of protrusions and a sealing side wall and is used for adsorbing and fixing a wafer; the thermal correction execution assembly comprises a substrate and an array composed of temperature execution units, each temperature execution unit comprises a heating / cooling element and a first temperature sensor, and the thermal correction execution assembly is used for controlling thermal deformation of the wafer to correct high-order overlay errors; the supporting assembly comprises an installation flange used for being fixedly connected with the vacuum suction cup and an array composed of second through holes. The piezoelectric ceramic driving assembly comprises an array composed of piezoelectric ceramic units, and the piezoelectric ceramic units penetrate through the second through holes and the first through holes in the thermal correction execution assembly to be in contact with the lower surface of the vacuum suction cup and are used for regulating and controlling the surface shape of the wafer; the protrusions, the temperature execution units, the second through holes and the array composed of the piezoelectric ceramic units correspond to one another.

Description

Technical Field

[0001] The present disclosure relates to the technical field of semiconductor equipment, and in particular to a thermal correction wafer stage, a photolithography device and a high-order overlay error correction method. Background Art

[0002] As the line width of semiconductor chips decreases, high-resolution overlay error control is an important challenge in the field of lithography. Mask and wafer deformation, non-uniformity of wafer stage movement, environmental factors, etc. will introduce alignment overlay errors. Currently, linear overlay error correction can be achieved by applying force actuators around the mask, such as translation, rotation, and magnification.

[0003] When the linear overlay error correction accuracy is not enough, it is necessary to correct the high-order overlay error. For the high-order overlay error correction achieved by controlling the lens in the prior art, the current lithography equipment can only support up to the third order, and there are multiple high-order terms that cannot be accurately corrected by controlling the lens alone.

[0004] High-order overlay error correction based on thermal actuators has higher precision requirements for the surface shape of the wafer. Therefore, the development of a wafer stage that takes into account both wafer surface shape control and high-order overlay error correction is of great value. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In view of the above problems, the present disclosure provides a thermal correction stage, a photolithography device and a high-order overlay error correction method, which are used to solve technical problems such as the difficulty in accurately correcting high-order overlay errors using traditional methods.

[0007] (II) Technical solution

[0008] The first aspect of the present disclosure provides a thermal correction wafer stage, which includes, from top to bottom: a vacuum suction cup, including an array composed of protrusions and a sealing side wall arranged around the periphery of the array, for adsorbing and fixing the wafer; a thermal correction execution component, including a substrate and an array composed of temperature execution units, each temperature execution unit including a heating / cooling element and a first temperature sensor, for controlling the thermal deformation of the wafer to correct high-order overlay errors; a support component, including a mounting flange for fixed connection to the vacuum suction cup and an array composed of second through holes; a piezoelectric ceramic drive component, including an array composed of piezoelectric ceramic units, the piezoelectric ceramic units pass through the second through holes and the first through holes on the thermal correction execution component and then contact the lower surface of the vacuum suction cup, for adjusting the surface shape of the wafer; wherein the array composed of protrusions, the array composed of temperature execution units, the array composed of second through holes and the array composed of piezoelectric ceramic units correspond to each other.

[0009] According to an embodiment of the present disclosure, the thickness of the vacuum suction cup is 1 to 2 mm; the material of the vacuum suction cup is any one of silicon carbide and aluminum nitride; and gaps are provided between adjacent protrusions in the vacuum suction cup to insulate each other.

[0010] According to an embodiment of the present disclosure, the substrate in the thermal correction actuator is a PCB board designed with a circuit; the heating / cooling element is a thermoelectric element, such as a Peltier, which is arranged on the lower surface of the substrate, and the temperature of each heating / cooling element is independently controlled; the first temperature sensor is a thermistor, which is arranged on the upper surface of the substrate.

[0011] According to an embodiment of the present disclosure, a heat transfer hole is further provided in the substrate, and the heat transfer hole is filled with a heat conductive material; the heat transfer hole is in contact with the heating / cooling element to quickly transfer heat to the protrusion.

[0012] According to an embodiment of the present disclosure, the heating / cooling element includes: a resistance heating wire, whose material is metal or conductive ceramic; a cooling water pipe, the liquid therein is any one of water and ethylene glycol; a heat conductive block, whose upper surface accommodates the resistance heating wire and the cooling water pipe for heat conduction; and a second temperature sensor, which is arranged on the lower surface of the heat conductive block.

[0013] According to an embodiment of the present disclosure, the support assembly also includes: at least four wire outlets for centrally leading out the circuit connection wires of the heating / cooling element and the first temperature sensor; a third through hole for accommodating the vacuum channel of the vacuum suction cup; and a cooling water pipe channel provided on the lower surface of the support assembly for releasing the heat generated by the heating / cooling element to the outside.

[0014] According to an embodiment of the present disclosure, the potential difference across each piezoelectric ceramic unit in the piezoelectric ceramic drive assembly is independently controlled to apply force to the vacuum chuck, thereby regulating the surface shape of the wafer; wherein the surface shape PV within an exposure field in the wafer is <10nm.

[0015] The second aspect of the present disclosure provides a lithography device, including: a thermal correction wafer stage according to the above-mentioned method, used to adjust the surface shape of the wafer and control the thermal deformation of the wafer to correct high-order overlay errors; an exposure light source; an alignment system, used to measure the overlay error; and a thermal correction control system, used to adjust the working state of the thermal correction execution component according to temperature load data to control the thermal deformation of the wafer and thereby correct the high-order overlay error.

[0016] The third aspect of the present disclosure provides a method for correcting high-order overlay errors, including: S1, after using a vacuum suction cup to absorb and fix the wafer, using a piezoelectric ceramic drive component to control the surface shape of the wafer; S2, establishing a grid coordinate system for an exposure field to obtain the thermal deformation matrix of the wafer; S3, using an alignment system to measure the overlay error in the exposure field, and calculating the temperature load control matrix data based on the overlay error; S4, adjusting the working state of the thermal correction execution component according to the temperature load control matrix data to control the thermal deformation of the wafer and thereby correct the high-order overlay error.

[0017] According to an embodiment of the present disclosure, it also includes: S5, using the alignment system to measure the overlay error after correcting the high-order overlay error; if the preset overlay accuracy is not met, the thermal deformation matrix is ​​corrected, and S3 to S5 are repeated until the preset overlay accuracy is met; if the preset overlay accuracy is met, the high-order overlay error correction process is ended.

[0018] (III) Beneficial effects

[0019] The thermal correction wafer stage, photolithography equipment and high-order overlay error correction method disclosed in the present invention utilize an array composed of temperature execution units in a thermal correction execution component to control the thermal deformation of the wafer to achieve correction of the overlay errors of the wafer in the X and Y directions, and can correct the overlay errors between exposure fields and within exposure fields, especially the high-order overlay errors, with higher accuracy. At the same time, in order to achieve efficient heat conduction, the vacuum suction cup is designed to have a very small thickness, which will cause deformation of the wafer during adsorption and affect the exposure effect. The surface shape of the wafer is regulated by a piezoelectric ceramic drive component to achieve correction of the deformation of the wafer in the Z direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematically shows an exploded view of a thermal correction wafer stage according to an embodiment of the present disclosure;

[0021] Figure 2 The cross-sectional structure diagram of the thermal correction wafer carrier according to the embodiment of the present disclosure is schematically shown;

[0022] Figure 3 A cross-sectional view schematically shows a state in which a vacuum chuck and a thermal correction actuator are in cooperation with each other according to an embodiment of the present disclosure;

[0023] Figure 4 Schematically shows a schematic diagram of the structure of a heating / cooling element according to an embodiment of the present disclosure;

[0024] Figure 5 The structural diagram of the support assembly according to the embodiment of the present disclosure is schematically shown;

[0025] Figure 6 The schematic diagram of the control process of the thermal correction control system according to the embodiment of the present disclosure is schematically shown;

[0026] Figure 7 The flowchart of the high-order overlay error correction method according to the embodiment of the present disclosure is schematically shown;

[0027] Figure 8 The schematic diagram of the structure of the grid coordinate system according to the embodiment of the present disclosure is shown;

[0028] Fig. 9 The schematic diagram of the arrangement structure of the temperature execution unit of the thermal correction execution component according to the embodiment of the present disclosure is shown;

[0029] Description of reference numerals:

[0030] 1. Wafer; 2. Vacuum suction cup; 21. Airtight side wall; 22. Protrusion; 23. Vacuum channel; 3. Thermal correction actuator; 31. Substrate; 32. Heating / cooling element; 33. First temperature sensor; 34. Heat transfer hole; 311. Resistance heating wire; 312. Cooling water pipe; 313. Heat conductive block; 314. Second temperature sensor; 4. Support assembly; 41. Mounting flange; 42. Wire outlet; 43. Second through hole; 44. Third through hole; 45. Cooling water pipe channel; 5. Piezoelectric ceramic drive assembly; 51. Piezoelectric ceramic unit. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0032] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0033] It should be noted that if directional indication is involved in the embodiments of the present disclosure, the directional indication is only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0034] The ordinal numbers used in the specification and claims, such as "first", "second", "third", etc., to modify the corresponding elements, do not themselves mean or represent any ordinal number of the element, nor do they represent the order of one element and another element, or the order of manufacturing methods. The use of these ordinal numbers is only used to clearly distinguish a component with a certain name from another component with the same name.

[0035] The present disclosure provides a thermal correction plate holder, see Figure 1-2 , from top to bottom, it includes: a vacuum suction cup 2, including an array composed of protrusions 22 and a sealing side wall 21 arranged around the outer periphery of the array, for adsorbing and fixing the wafer 1; a thermal correction execution component 3, including a substrate 31 and an array composed of temperature execution units, each temperature execution unit includes a heating / cooling element 32 and a first temperature sensor 33, for controlling the thermal deformation of the wafer 1 to correct the high-order overlay error; a support component 4, including a mounting flange 41 for fixed connection with the vacuum suction cup 2 and an array composed of second through holes 43; a piezoelectric ceramic drive component 5, including an array composed of piezoelectric ceramic units 51, the piezoelectric ceramic units 51 pass through the second through holes 43 and the first through holes on the thermal correction execution component 3 and then contact with the lower surface of the vacuum suction cup 2, for adjusting the surface shape of the wafer 1; wherein, the array composed of protrusions 22, the array composed of temperature execution units, the array composed of second through holes 43 and the array composed of piezoelectric ceramic units 51 correspond to each other.

[0036] The thermal correction wafer stage has a multi-layer structure, integrating functions such as vacuum adsorption, high-order overlay error correction, and wafer surface shape control. Among them, the array composed of temperature execution units in the thermal correction execution component 3 is used to control the thermal deformation of the wafer 1 to achieve the correction of the wafer X-direction and Y-direction overlay error, and can correct the overlay error between exposure fields and within the exposure field, especially the high-order overlay error, with higher accuracy; at the same time, in order to achieve efficient heat conduction, the vacuum suction cup 2 is designed to be very thin, which will cause the wafer 1 to deform during adsorption and affect the exposure effect. The piezoelectric ceramic drive component 5 is used to control the surface shape of the wafer 1 to achieve the correction of the wafer Z-direction deformation.

[0037] On the basis of the above embodiment, the thickness of the vacuum suction cup 2 is 1-2 mm; the material of the vacuum suction cup 2 is any one of silicon carbide and aluminum nitride; and gaps are provided between adjacent protrusions 22 in the vacuum suction cup 2 for mutual heat insulation.

[0038] The vacuum chuck 2 includes a sealing side wall 21 and a plurality of protrusions 22 arranged in the area surrounded by the sealing side wall 21. The protrusions 22 may be cylindrical. The wafer 1 can be attached to the upper surface of the vacuum chuck 2 and contact the surface of the protrusions 22. Under the action of vacuum, the wafer 1 and the vacuum chuck 2 are tightly attached and a closed vacuum chamber is formed between the two, thereby fixing the wafer 1. The vacuum chuck 2 can locally transfer the heat received from the thermal correction actuator 3 to the wafer 1, thereby controlling the thermal deformation of the wafer 1 and correcting the high-order overlay error. There is a certain gap between the protrusions 22 of the vacuum chuck 2, which can realize the function of heat insulation from each other, thereby performing local temperature control on the wafer 1. In order to achieve efficient heat conduction, the thickness of the wafer support surface formed by the vacuum chuck 2 should be set to be significantly smaller than the thickness of the existing conventional wafer support surface, for example, 1 to 2 mm.

[0039] Based on the above embodiments, Figure 3 As shown, the substrate 31 in the thermal correction actuator 3 is a PCB board designed with a circuit; the heating / cooling element 32 is a thermoelectric element, which is arranged on the lower surface of the substrate 31, and the temperature of each heating / cooling element 32 is independently controlled; the first temperature sensor 33 is a thermistor, which is arranged on the upper surface of the substrate 31.

[0040] The thermal correction execution component 3 includes a substrate 31 and a temperature execution unit composed of a plurality of first temperature sensors 33 and a heating / cooling element 32. The temperature of each heating / cooling element 32 can be independently controlled. The substrate 31 can be a PCB board designed with a circuit; the heating / cooling element 32 can be a thermoelectric element, which is welded on the lower surface of the substrate 31 to form a conductive circuit, and realizes the heating and cooling functions by changing the direction of current flow; the first temperature sensor 33 can be a thermistor, which is welded on the upper surface of the substrate 31 to measure the temperature of the heating / cooling element 32.

[0041] The control component performs feedback adjustment on the temperature of each heating / cooling element 32 in the temperature execution unit, so that the thermal correction execution component 3 can realize the thermal deformation correction function. During the heating or cooling process, the first temperature sensor 33 can monitor the temperature change of each heating / cooling element 32 in the temperature execution unit in real time and transmit the data to the control component. The control component adjusts the working state of the heating / cooling element 32 according to the set temperature range and temperature change rate and other temperature load data to achieve a stable temperature control effect.

[0042] The array of temperature execution units in the thermal correction execution component 3 can be used in various temperature control systems to achieve independent temperature control of multiple regions in a small area. The temperature matrix for correcting high-order overlay errors is calculated based on the thermal deformation matrix, and high-order overlay errors can be corrected quickly and efficiently, which can be applied to high-precision deformation correction systems in other fields.

[0043] On the basis of the above embodiment, a heat transfer hole 34 is further provided in the substrate 31 , and the heat transfer hole 34 is filled with a heat conductive material; the heat transfer hole 34 is in contact with the heating / cooling element 32 for quickly transferring heat to the protrusion 22 .

[0044] like Figure 3 As shown, a heat transfer hole 34 is provided on the substrate 31, and a heat conductive material (such as copper) is filled into the heat transfer hole 34, so that the temperature of the heating / cooling element 32 is quickly transferred to the upper surface of the protrusion 22 in the vacuum suction cup 2, thereby achieving the purpose of heating / cooling the wafer 1.

[0045] According to another embodiment of the present disclosure, the heating / cooling element 32 includes: a resistance heating wire 311, whose material is metal or conductive ceramic; a cooling water pipe 312, whose liquid is any one of water and ethylene glycol; a heat conductive block 313, whose upper surface accommodates the resistance heating wire 311 and the cooling water pipe 312 for heat conduction; and a second temperature sensor 314, which is arranged on the lower surface of the heat conductive block 313.

[0046] The heating / cooling element 32 may be Figure 4 In the structure shown, the resistance heating wire 311 and the cooling water pipe 312 are embedded in the heat conductive block 313, and the second temperature sensor 314 is attached to the back of the heat conductive block 313 to measure the temperature of the heating / cooling element 32. The resistance heating wire 311 may include a metal such as tungsten, copper, or nickel-chromium alloy, or may include conductive ceramics such as tungsten carbide, titanium nitride, etc. The liquid in the cooling water pipe 312 may include water, ethylene glycol, etc.

[0047] On the basis of the above embodiment, the support assembly 4 also includes: at least four wire outlets 42, which are used to centrally lead out the circuit connection wires of the heating / cooling element 32 and the first temperature sensor 33; a third through hole 44, which is used to accommodate the vacuum channel 23 of the vacuum suction cup 2; a cooling water pipe channel 45, which is arranged on the lower surface of the support assembly 4, and is used to release the heat generated by the heating / cooling element 32 to the outside.

[0048] The support assembly 4 is mechanically connected and fixed to the vacuum chuck 2 through the mounting flange 41, and the thermal correction actuator 3 is sandwiched between the two. The wires of the thermal correction actuator 3 are centrally led out from the wire outlet 42 of the support assembly 4, such as Figure 5 As shown in (a), there are four wire outlets 42, for example, which are evenly distributed on the periphery of the array formed by the second through holes 43. The first temperature sensor 33 and the heating / cooling element 32 in the temperature execution unit are welded on the substrate 31 arranged with the circuit, and the wires are centrally led out at the edge of the support assembly 4, which reduces the failure rate of the temperature execution unit and improves the connection efficiency.

[0049] like Figure 5 As shown in (b), the back of the support assembly 4 can be further designed with a cooling water pipe channel 45, which runs through the bottom of the heating / cooling element 32, and releases the heat generated by the heating / cooling element 32 to the outside by water cooling. The temperature of the support assembly 4 can be controlled by adjusting the flow rate and temperature of the cooling water by the control assembly.

[0050] Based on the above embodiment, the potential difference across each piezoelectric ceramic unit 51 in the piezoelectric ceramic drive assembly 5 is independently controlled to apply force to the vacuum suction cup 2, thereby regulating the surface shape of the wafer 1; wherein the surface shape within an exposure field in the wafer 1 is preferably controlled to PV<10nm.

[0051] The piezoelectric ceramic drive assembly 5 is used to control the surface shape of the wafer 1 to avoid the adsorption deformation of the wafer 1 due to the small thickness of the wafer support surface, which affects the exposure effect. The piezoelectric ceramic drive assembly 5 is installed below the support assembly 4, and can be regulated only for one exposure field. After the exposure field is switched, the piezoelectric ceramic drive assembly 5 exits under the control of the motor and moves to the corresponding exposure field before working. However, the present disclosure is not limited to this, and multiple piezoelectric ceramic drive assemblies 5 can also be set according to the number of exposure fields for separate control.

[0052] The surface of the piezoelectric ceramic drive component 5 is provided with an array composed of a plurality of piezoelectric ceramic units 51. The external circuit independently applies a potential difference to both ends of each piezoelectric ceramic unit 51, so that the piezoelectric ceramic unit 51 is deformed independently. The piezoelectric ceramic unit 51 passes through the through holes respectively provided on the support component 4 and the thermal correction actuator 3 and directly contacts the lower surface of the vacuum suction cup 2, thereby regulating the surface shape of the wafer 1 placed thereon. Preferably, the surface shape within an exposure field (e.g., 26mm×33mm) needs to be regulated to PV<10nm. The piezoelectric ceramic drive component can realize the control of the wafer adsorption surface shape, solving the problems of easy deformation and poor flatness caused by the small thickness of the support surface of the vacuum suction cup of the wafer stage.

[0053] The thermal correction wafer stage disclosed in the present invention can achieve high-order overlay error correction by controlling the thermal deformation of the wafer, and can also use a piezoelectric ceramic drive component to regulate the surface shape of the wafer to ensure exposure and overlay quality.

[0054] The present disclosure also provides a lithography device, including: according to the above-mentioned thermal correction wafer stage, it is used to adjust the surface shape of the wafer 1 and control the thermal deformation of the wafer 1 to correct the high-order overlay error; an exposure light source; an alignment system, used to measure the overlay error; a thermal correction control system, used to adjust the working state of the thermal correction execution component 3 according to the temperature load data to control the thermal deformation of the wafer 1 and then correct the high-order overlay error.

[0055] The present disclosure also provides a lithography device including the above-mentioned thermal correction wafer stage, and the lithography device at least includes basic configurations such as an exposure light source, an alignment system, and a thermal correction control system. Figure 6As shown, the key to the temperature control of the heating / cooling element 32 is to accurately monitor the temperature and perform feedback adjustment. During the heating or cooling process, the first temperature sensor 33 can monitor the temperature change of the target object in real time and transmit the data to the thermal correction control system. The thermal correction control system adjusts the working state of the heating / cooling element 32 according to the set temperature range and temperature change rate, such as the temperature adjustment range of -20℃~+20℃ and the temperature change rate of 0.1℃, to achieve a stable temperature control effect. Among them, when the temperature load is set (the temperature load is within the adjustment range), the thermal correction control system adjusts the working state of the heating / cooling element 32 to increase or decrease the temperature according to the temperature change rate, so that the temperature measured by the first temperature sensor 33 reaches the specified temperature load.

[0056] The present disclosure also provides a high-order overlay error correction method, such as Figure 7 As shown, it includes: S1, after using the vacuum suction cup 2 to absorb and fix the wafer 1, using the piezoelectric ceramic driving component 5 to control the surface shape of the wafer 1; S2, establishing a grid coordinate system for an exposure field to obtain the thermal deformation matrix of the wafer 1; S3, using the alignment system to measure the overlay error in the exposure field, and calculating the temperature load control matrix data according to the overlay error; S4, adjusting the working state of the thermal correction execution component 3 according to the temperature load control matrix data to control the thermal deformation of the wafer 1 and then correct the high-order overlay error.

[0057] Step S1: The wafer 1 is attached to the upper surface of the vacuum chuck 2, and the space enclosed by the airtight side wall 21 and the wafer 1 is evacuated through the central vacuum channel 23, and the wafer 1 is adsorbed and fixed on the upper surface of the protrusion 22. The piezoelectric ceramic drive assembly 5 is moved to the area to be adjusted, and a potential difference is applied to both ends of each piezoelectric ceramic unit 51 through the thermal correction control system of the lithography equipment to adjust the wafer 1 to the desired surface shape.

[0058] Step S2: using the alignment system of the lithography equipment to measure the overlay error δ0. The wafer 1 includes a front layer pattern, and the alignment system obtains the overlay error by measuring the deviation between the overlay mark of the current mask used for lithography and the overlay mark on the front layer pattern in the X direction and the Y direction.

[0059] Establish a grid coordinate system. Take the center of the exposure field as the origin and establish Figure 8 The coordinate system is shown in Figure 1, and the grid areas and grid nodes are numbered. For example, the grid areas are defined as A1, A2, ... A48, and the grid nodes are defined as N1, N2, ... N35. Each grid node can be used as a marking point.

[0060] Use the alignment system to measure the overlay error δ in the X and Y directions of the mark point xi ,δ yi δ xi ,δyi is a high-order overlay error including second-order and third-order terms. It can be represented by the following parameter model:

[0061]

[0062] Among them, k1…k 19 is the overlay error model coefficient, the overlay error δ in the X direction of the measuring point x It is recorded as the root mean square of the overlay error of all grid nodes in the X direction and the overlay error in the Y direction δ y It is recorded as the root mean square of the Y-direction overlay error of all grid nodes.

[0063] Step S3: Calculate the temperature load control matrix.

[0064] Before calculating the temperature load control matrix, it is necessary to obtain the thermal deformation matrix C of the wafer.

[0065] The relationship between the temperature load T applied in the wafer exposure field and the deformation Δ at the measuring point is shown in formula (1):

[0066] C×T=Δ (1)

[0067] Where C is the wafer thermal deformation matrix. The thermal deformation matrix C can be calculated using finite element software by i The unit temperature load is applied to the area to calculate the thermal deformation in the X and Y directions of all measuring points in the entire field, and the column matrix C is obtained. ix and C iy , the column matrix combination obtains the thermal deformation matrix C x and C y In addition, the thermal deformation matrix C of the wafer can also be obtained through experimental testing methods.

[0068]

[0069] The overlay error δ is the deformation Δ at the measuring point of the pre-corrected wafer.

[0070] According to the overlay error δ and the wafer thermal deformation matrix C obtained in advance, the optimal solution T of equation group (3) is obtained by solving the minimum residual w between the overlay error and the deformation at the measuring point position. The optimal solution T is the temperature load control matrix. In the first calculation, the overlay error δ0 measured in step S2 is used as the overlay error δ for calculation.

[0071] w≥δ-C×T

[0072] w≥C×T-δ (3)

[0073] T1≤T≤T2

[0074] Wherein, T1 and T2 are the lower limit and upper limit of temperature control respectively. The solution of the temperature load control matrix when the residual is minimum in step S2 includes the least square method.

[0075] Step S4: input the temperature load control matrix T obtained in step S3 to the thermal correction control system. The thermal correction control system adjusts the deformation of the surface of the wafer 1 by independently controlling the temperature of each heating / cooling element 32 to compensate for the high-order overlay error.

[0076] On the basis of the above embodiment, it also includes: S5, using the alignment system to measure the overlay error after correcting the high-order overlay error; if the preset overlay accuracy is not met, the thermal deformation matrix is ​​corrected, and S3 to S5 are repeated until the preset overlay accuracy is met; if the preset overlay accuracy is met, the high-order overlay error correction process is ended.

[0077] Step S5: Use the alignment system to measure the corrected overlay error δ1 again to verify whether it meets the required overlay accuracy, for example, the accuracy requirement of the high-order overlay error correction is less than 5nm. If the required overlay accuracy is met, the high-order overlay error correction process is terminated; if not, the wafer thermal deformation matrix C is corrected by adding a small correction amount to the unit temperature deformation variable, that is, the element in the wafer thermal deformation matrix C, and correcting it in the direction of reducing the overlay error to converge the calculation, and obtaining C j Then it is used as the new wafer thermal deformation matrix C, and the corrected overlay error δ1 is substituted into formula (3) as the new overlay error δ, and steps S3 to S5 are repeated to obtain the overlay error δ2 of this iteration. The iteration is repeated multiple times until the required overlay accuracy is met.

[0078] The high-order overlay error correction method disclosed in the present invention calculates a temperature load control matrix for correcting the high-order overlay error based on a thermal deformation matrix, and can provide timely feedback and correct the high-order overlay error quickly and efficiently.

[0079] The present disclosure is further described below through specific implementation methods. The above-mentioned thermal correction wafer stage, photolithography equipment and high-order overlay error correction method are specifically described in the following embodiments. However, the following embodiments are only used to illustrate the present disclosure, and the scope of the present disclosure is not limited thereto.

[0080] This embodiment provides a thermal correction substrate table, referring to Figure 1 and Figure 2 , including: a vacuum suction cup 2, a thermal correction actuator component 3, a support component 4 and a piezoelectric ceramic drive component 5.

[0081] The vacuum chuck 2 is disc-shaped, and the wafer 1 can be attached to the upper surface of the vacuum chuck 2. The vacuum chuck 2 is provided with a sealing side wall 21 and a cylindrical protrusion 22, and the sealing side wall 21 is arranged around the cylindrical protrusion 22 to form a vacuum chamber; the vacuum channel 23 is pressurized to form a vacuum chamber in the area enclosed by the wafer 1 and the vacuum chuck 2.

[0082] The vacuum chuck 2 can transfer the heat received from the thermal correction actuator 3 to the local part of the wafer 1 to heat or cool the wafer 1 and control the thermal deformation of the wafer 1. Among them, the cylindrical protrusions 22 of the vacuum chuck 2 can support the wafer 1 to ensure the flatness of the wafer 1; there is a certain gap between the cylindrical protrusions 22, which can realize the function of heat insulation, and then locally control the temperature of the upper surface of the vacuum chuck 2; the cylindrical protrusions 22 of the vacuum chuck 2 and the base of the vacuum chuck 2 have a small thickness to ensure that the temperature can be quickly transferred to the wafer 1 and reach a steady state; the vacuum chuck 2 can be made of materials with good thermal conductivity and small thermal deformation, such as silicon carbide, aluminum nitride, etc.

[0083] Figure 3 The figure shows a cross-sectional view of the vacuum chuck 2 and the thermal correction actuator 3 in a mating state. The thermal correction actuator 3 includes a substrate 31 and a plurality of temperature actuator units, each of which includes a heating / cooling element 32 and a first temperature sensor 33. The plurality of heating / cooling elements 32 can be independently controlled to distribute heat locally in the vacuum chuck 2. A groove is provided on the vacuum chuck 2 to accommodate the first temperature sensor 33.

[0084] The substrate 31 includes materials such as a PCB board, etc. The circuit of the temperature sensor 33 is arranged on the upper surface of the substrate 31, and the circuit of the heating / cooling element 32 is arranged on the lower surface.

[0085] The arrangement of the temperature execution unit of the thermal correction execution component 3 is as follows: Fig. 9 As shown. There are 9 exposure fields designed on wafer 1, each with a size of 26mm×33mm. Fig. 9 The area enclosed by the thick solid line is the exposure field. In order to achieve overlay error correction in the entire field, a 39mm×44mm area around the exposure field is selected to apply a temperature load using a temperature execution array. Each area is divided into 6×8 small areas. The corresponding lower surface of the vacuum suction cup 2 and the substrate 31 are also divided into small areas of the same number and size. The temperature execution units of the thermal correction execution component 3 are distributed in each small area of ​​the substrate 31.

[0086] The heating / cooling element 32 includes a thermoelectric element, which can perform heat absorption and heat release using the Peltier effect. Specifically, the thermoelectric element has positive and negative poles, is welded on the substrate 31, switches between heat absorption and heat release according to the direction of the current, and can control the amount of heat absorption and heat release according to the amount of the current. The first temperature sensor 33 includes a thermistor, which is welded on the substrate 31 and can measure the temperature of the thermoelectric element.

[0087] Figure 5 (a) shows a front structural schematic diagram of the support assembly 4. Figure 5 (b) is a schematic structural diagram of the back side of the support assembly 4. The support assembly 4 is mechanically connected and fixed to the vacuum chuck 2 through the mounting flange 41, and the thermal correction actuator 3 is sandwiched between the two.

[0088] The support assembly 4 is provided with four wire outlets 42, which centrally lead out the circuit connection wires between the first temperature sensor 33 and the heating / cooling element 32; a third through hole 44 is provided in the center of the support assembly, and the vacuum channel 23 of the vacuum suction cup 2 passes through the third through hole 44. The support assembly 4 is also provided with a cooling water pipe channel 45, which runs through the heating / cooling elements 32 and releases the heat generated by the heating / cooling elements 32 to the outside by water cooling. The temperature of the support assembly 4 can be controlled by adjusting the flow rate and temperature of the cooling water through the thermal correction control system.

[0089] like Figure 2 As shown, the piezoelectric ceramic drive assembly 5 is composed of a plurality of piezoelectric ceramic units 51, a second through hole 43 is provided on the support assembly 4, and a first through hole is also provided on the substrate 31 of the thermal correction actuator 3. The piezoelectric ceramic unit 51 passes through the second through hole 43 and the first through hole to contact the bottom of the vacuum suction cup 2. Each piezoelectric ceramic unit 51 is independently connected to the external circuit through an electrode line, and the external circuit applies a potential difference to both ends of each piezoelectric ceramic unit 51 independently, so that the piezoelectric ceramic unit 51 is deformed independently, and a force is applied to the vacuum suction cup 2, thereby regulating the surface shape of the wafer 1.

[0090] Among them, the piezoelectric ceramic drive assembly 5 is only regulated for one exposure field. After the exposure field is switched, the piezoelectric ceramic drive assembly 5 moves to the corresponding exposure field under the control of the thermal correction control system and the motor and then works. The piezoelectric ceramic drive assembly 5 has 6×8 piezoelectric drive units, which is consistent with the regional division of the exposure field.

[0091] This embodiment also provides a high-order overlay error correction method, including steps S01 to S05:

[0092] Step S01: Attach the wafer 1 to the upper surface of the vacuum chuck 2, evacuate the space enclosed by the airtight side wall 21 and the wafer 1 through the central vacuum channel 23, and adsorb and fix the wafer 1 on the cylindrical protrusion 22. Move the piezoelectric ceramic drive assembly 5 to the area to be adjusted, apply a potential difference to both ends of each piezoelectric ceramic unit 51 through the thermal correction control system of the lithography equipment, and adjust the surface shape of the wafer 1 within an exposure field (e.g., 26mm×33mm) to PV<10nm. This is equivalent to the above step S1.

[0093] Step S02: using an alignment system of a lithography device to measure an overlay error δ0.

[0094] Establish a grid coordinate system. Take the center of the exposure field as the origin and establish Figure 8 The grid coordinate system is shown in Figure 1, and the grid areas and grid nodes are numbered. The grid areas are defined as A1, A2, ... A48, and the grid nodes are defined as N1, N2, ... N35. Each grid node can be used as a marking point.

[0095] Use the alignment system to measure the overlay error δ in the X and Y directions of the mark point xi ,δ yi The more marking points there are, the more evenly they are distributed in the exposure field, and the more accurate the final calculation result will be.

[0096] δ xi ,δ yi It is a high-order overlay error including second-order and third-order terms, which can be expressed by the following parameter model:

[0097]

[0098] A high-order overlay error model is selected as an example for illustration. The lens can compensate for the second order (k7, k 12 ) or third order (k 13 ) Overlay error, k8, k 10 , k 11 , k 14 , k 16 , k 19 This can be achieved by adjusting the scanning direction of the wafer stage in the Y direction, but k9, k 15 , k 17 , k 18 , k 20 It is not possible to achieve this at present. Therefore, this embodiment selects k 17 =1×10 -8 , k 18 =1×10 -8, and the other parameters are all equal to 0 for illustration. Before correction, the root mean square of the overlay error in the X direction at the grid node is 14 nm, and the root mean square of the overlay error in the Y direction is 12 nm. This is equivalent to the above step S2.

[0099] Step S03: Calculate the temperature load control matrix C.

[0100] By being alone in A i The unit temperature load is applied to the region to calculate the thermal deformation in the X and Y directions of all grid node positions in the entire field, and the column matrix C is obtained. ix and C iy , the column matrix is ​​combined to obtain the thermal deformation matrix C x and C y . x and C y Combining the matrix,

[0101] According to the overlay error δ measured in step S02 and the wafer thermal deformation matrix C obtained in advance, the optimal solution T of equation group (2) is obtained by solving the minimum residual w. The minimum residual is the overlay error, and the optimal solution T is the temperature load control matrix.

[0102] For example, the solution algorithm may include the least square method, and the temperature load control matrix obtained is T=[10.9, 4.9, 6.8, 4.9, 7.3...]° C. This is equivalent to the above step S3.

[0103] Step S04: Input the temperature load control matrix T obtained in step S03 to the thermal correction control system, which independently controls the temperature of each heating / cooling element 32 to adjust the deformation of the surface of the wafer 1 to compensate for the high-order overlay error. This is equivalent to the above step S4.

[0104] Step S05: Use the alignment system to measure the corrected overlay error again, the X-direction overlay error w 1x =0.07nm, Y direction overlay error w 1y =0.09nm, which meets the accuracy requirement of high-order overlay error correction of less than 5nm. This is equivalent to the above step S5.

[0105] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the protection of the present disclosure.

Claims

1. A thermal correction sheet holding table, characterized in that: From top to bottom, they include: A vacuum suction cup (2), comprising an array of protrusions (22) and a sealing side wall (21) arranged around the periphery of the array, for sucking and fixing the wafer (1); A thermal correction execution component (3) comprises a substrate (31) and an array of temperature execution units, each of the temperature execution units comprising a heating / cooling element (32) and a first temperature sensor (33), for controlling thermal deformation of the wafer (1) to correct high-order overlay errors; A support assembly (4) comprising a mounting flange (41) for fixedly connecting to the vacuum suction cup (2) and an array of second through holes (43); A piezoelectric ceramic drive assembly (5), comprising an array of piezoelectric ceramic units (51), wherein the piezoelectric ceramic units (51) pass through the second through hole (43) and the first through hole on the thermal correction actuator (3) and then contact the lower surface of the vacuum suction cup (2), so as to adjust the surface shape of the wafer (1); The array composed of protrusions (22), the array composed of temperature execution units, the array composed of second through holes (43) and the array composed of piezoelectric ceramic units (51) correspond to each other.

2. The thermal correction substrate holder according to claim 1, characterized in that: The thickness of the vacuum suction cup (2) is 1 to 2 mm; the material of the vacuum suction cup (2) is any one of silicon carbide and aluminum nitride; Gaps are provided between adjacent protrusions (22) in the vacuum suction cup (2) to provide mutual thermal insulation.

3. The thermal correction substrate holder according to claim 1, characterized in that: The substrate (31) in the thermal correction actuator (3) is a PCB board designed with circuits; The heating / cooling element (32) is a thermoelectric element, which is arranged on the lower surface of the substrate (31), and the temperature of each heating / cooling element (32) is independently controlled; The first temperature sensor (33) is a thermistor and is disposed on the upper surface of the substrate (31).

4. The thermal correction substrate holder according to claim 3, characterized in that: The substrate (31) is also provided with a heat transfer hole (34), and the heat transfer hole (34) is filled with a heat conductive material; The heat transfer holes (34) are in contact with the heating / cooling element (32) for quickly transferring heat to the protrusions (22).

5. The thermal correction substrate holder according to claim 1, characterized in that: The heating / cooling element (32) comprises: The resistance heating wire (311) is made of metal or conductive ceramic; A cooling water pipe (312), wherein the liquid is any one of water and ethylene glycol; A heat conducting block (313), the upper surface of which contains the resistance heating wire (311) and the cooling water pipe (312) for heat conduction; The second temperature sensor (314) is arranged on the lower surface of the heat conducting block (313).

6. The thermal correction substrate holder according to claim 1, characterized in that: The support assembly (4) further comprises: At least four wire outlets (42) for centrally leading out the circuit connection wires of the heating / cooling element (32) and the first temperature sensor (33); A third through hole (44) for accommodating a vacuum channel (23) of the vacuum suction cup (2); A cooling water pipe channel (45) is provided on the lower surface of the support assembly (4) and is used to release the heat generated by the heating / cooling element (32) to the outside.

7. The thermal correction substrate holder according to claim 1, characterized in that: The potential difference between the two ends of each piezoelectric ceramic unit (51) in the piezoelectric ceramic drive assembly (5) is independently controlled to apply a force to the vacuum chuck (2), thereby regulating the surface shape of the wafer (1); Wherein, the surface shape PV in an exposure field of the wafer (1) is less than 10 nm.

8. A lithography apparatus, characterized in that: include: The thermal correction wafer stage according to any one of claims 1 to 7 is used to adjust the surface shape of the wafer (1) and control the thermal deformation of the wafer (1) to correct high-order overlay errors; Exposure light source; Alignment system for measuring overlay error; A thermal correction control system is used to adjust the working state of a thermal correction execution component (3) according to temperature load data to control the thermal deformation of the wafer (1) and thereby correct high-order overlay errors.

9. A high-order overlay error correction method, characterized in that: include: S1, after using a vacuum suction cup (2) to absorb and fix a wafer (1), using a piezoelectric ceramic driving component (5) to adjust the surface shape of the wafer (1); S2, establishing a grid coordinate system for an exposure field to obtain a thermal deformation matrix of the wafer (1); S3, measuring the overlay error in the exposure field by using an alignment system, and calculating temperature load control matrix data according to the overlay error; S4, adjusting the working state of the thermal correction execution component (3) according to the temperature load control matrix data to control the thermal deformation of the wafer (1) and thereby correct the high-order overlay error.

10. The high-order overlay error correction method according to claim 9, characterized in that: Also includes: S5, using the alignment system to measure the overlay error after correcting the high-order overlay error; if the preset overlay accuracy is not met, the thermal deformation matrix is ​​corrected, and S3 to S5 are repeated until the preset overlay accuracy is met; if the preset overlay accuracy is met, the high-order overlay error correction process is terminated.

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