Photolithography machine object plane measurement method and photolithography machine optical system

Abstract

This application provides a method for measuring the surface area of ​​a lithography machine and an optical system for the lithography machine, relating to the field of semiconductor manufacturing technology. The method includes: acquiring multiple stage heights measured by a z-axis interferometer at a preset frequency, and the initial surface height of the silicon wafer measured by a leveling and focusing system at a preset frequency, wherein the preset frequency is less than or equal to a preset threshold; performing error compensation on the measured height of each spot in each measurement cycle based on the stage height of each measurement cycle, obtaining the compensated height of each spot in each measurement cycle; obtaining the target height of each spot based on the compensated height of each spot in each measurement cycle; and performing fitting processing on all target heights to determine the actual surface shape information of the silicon wafer. This application, through multiple measurements combined with error compensation, effectively removes systematic and random errors caused by stage instability, improving the measurement accuracy of the leveling and focusing system and the authenticity of the silicon wafer surface shape information.

Description

Technical Field

[0001] This application relates to the field of semiconductor manufacturing technology, and more specifically, to a method for measuring the surface of a lithography machine and an optical system for a lithography machine. Background Technology

[0002] In current semiconductor manufacturing processes, leveling and focusing systems are widely used to ensure that the silicon wafer surface achieves the required flatness and focal position. Existing leveling and focusing systems determine the silicon wafer surface shape information by measuring and fitting the height data of the light spots distributed on the silicon wafer surface.

[0003] However, environmental noise and instrument vibration have a significant impact on low- and mid-frequency vibrations, especially in the low-frequency range. This can lead to increased errors in the surface characteristic parameters of the silicon wafer output by the leveling and focusing system, thus limiting measurement accuracy. Furthermore, since the silicon wafer is placed on a motion stage, and the stage itself inevitably vibrates, this vibration directly affects the measurement accuracy of the leveling and focusing system. Consequently, the obtained silicon wafer surface shape information is not entirely accurate and reliable, failing to accurately reflect the actual surface characteristics of the silicon wafer. Summary of the Invention

[0004] The purpose of this application is to address the shortcomings of the prior art by providing a method for measuring the surface of a lithography machine and an optical system for a lithography machine. This solves the problem that in the prior art, the silicon wafer is placed on a moving stage, and the moving stage itself inevitably vibrates. The vibration of the moving stage directly affects the measurement accuracy of the leveling and focusing system, resulting in the final silicon wafer surface shape information being unreliable and unable to accurately reflect the actual surface characteristics of the silicon wafer.

[0005] To achieve the above objectives, the technical solutions adopted in the embodiments of this application are as follows:

[0006] In a first aspect, embodiments of this application provide a method for measuring the surface of a lithography machine, the method comprising:

[0007] The heights of multiple motion stages measured by the z-axis interferometer of the motion stage at a preset frequency are obtained, and the initial surface height of the silicon wafer measured by the leveling and focusing system at the preset frequency is obtained, wherein the preset frequency is less than or equal to a preset threshold, and the initial surface height includes the measured heights of multiple light spots.

[0008] Error compensation is performed on the measurement height of each light spot in each measurement cycle based on the height of the motion table in each measurement cycle, so as to obtain the compensated height of each light spot in each measurement cycle.

[0009] The target height of each light spot is obtained based on the compensated height of each light spot in each measurement round;

[0010] The target height of all light spots is fitted to determine the actual surface shape information of the silicon wafer, which includes focal length information and tilt information.

[0011] As one possible implementation, the step of compensating for the measurement height of each light spot in each measurement cycle based on the motion table height in each measurement cycle to obtain the compensated height of each light spot in each measurement cycle includes:

[0012] Based on the height of the motion table and the stable height of the motion table in the current measurement cycle, the jitter height of the motion table in the current measurement cycle is determined, where the height of the motion table is the measurement height obtained by the motion table z-axis interferometer;

[0013] Error compensation is performed on the measurement height of the current spot in the current measurement cycle based on the jitter height of the motion stage in the current measurement cycle to obtain the compensated height of the current spot in the current cycle. The compensated height represents the stable height of the silicon wafer surface relative to the ideal focal plane of the lithography machine's optical system.

[0014] As one possible implementation, determining the motion table jitter height for the current measurement round based on the motion table height and the stable height of the motion table includes:

[0015] Based on formula The vibration height of the motion table is calculated.

[0016] in, This indicates the measured height obtained by the z-axis interferometer of the motion stage. This indicates the stable height of the motion platform. This indicates the height of the vibration of the motion table.

[0017] As one possible implementation, the step of performing error compensation on the measurement height of the current light spot in the current measurement round based on the jitter height of the motion table to obtain the compensated height of the current light spot in the current round includes:

[0018] Based on formula The compensated height of the current light spot is calculated;

[0019] in, This indicates the current measurement height of the light spot, which is the measurement height of the silicon wafer surface relative to the ideal focal plane of the lithography machine's optical system. This indicates the current measurement height of the light spot, which is also the stable height of the silicon wafer surface relative to the ideal focal plane of the lithography machine's optical system. This indicates the height of the vibration of the motion table.

[0020] As one possible implementation, the process of fitting the target height of all light spots to determine the actual surface shape information of the silicon wafer, the actual surface shape information including focal length information and tilt information, including:

[0021] The target height of the multiple light spots is fitted using the least squares method to determine the actual surface shape information of the silicon wafer within the light spot range of the leveling and focusing system.

[0022] As one possible implementation, the target height of the light spot includes: the height of the light spot on the silicon wafer surface. coordinate, Coordinates and coordinate positions Silicon wafer height at the location ;

[0023] The process of fitting the target height of the multiple light spots using the least squares method to determine the actual surface shape information of the silicon wafer within the light spot range of the leveling and focusing system includes:

[0024] The light spots on the silicon wafer surface coordinate, Coordinates and coordinate positions Silicon wafer height at the location Enter the formulas respectively A plane fitting is performed to obtain the least squares solution; where... Indicates the coordinate position The height of the silicon wafer at that location, Indicates the first parameter. Indicates the second parameter. Indicates the third parameter. This represents the x-coordinate of the light spot on the silicon wafer surface. This represents the ordinate of the light spot on the silicon wafer surface;

[0025] The first parameter corresponding to the least squares solution is used as the focal length information, and the second and third parameters corresponding to the least squares solution are used as the tilt information.

[0026] As one possible implementation, before obtaining the initial surface height of the silicon wafer measured by the leveling and focusing system at the preset frequency, the method further includes:

[0027] The leveling and focusing system is controlled to emit multiple light spots toward the base plate;

[0028] A planar consistency test is performed on multiple light spots emitted onto the base plate. If the planar consistency test fails, the zero plane of the leveling and focusing system is adjusted.

[0029] As one possible implementation, the planar consistency detection of multiple light spots emitted onto the base plate, and the adjustment of the null plane of the leveling and focusing system if the planar consistency detection fails, includes:

[0030] Step A: Select one light spot from the multiple light spots of the leveling and focusing system as the effective light spot;

[0031] Step B: Move the micro-motion stage to move the center position of the preset flat area in the base plate to the effective light spot;

[0032] Step C: Obtain the single-point height value obtained by the leveling and focusing system measuring the single-point height of the effective light spot;

[0033] Step D: Repeat steps A-C above to obtain the single-point height value of each light spot;

[0034] Step E: Determine the height difference value of each light spot relative to the center position based on the single-point height value of each light spot. If the height difference value is greater than a preset threshold, adjust the zero plane of the leveling and focusing system.

[0035] Secondly, this application provides a lithography machine optical system, which includes at least: a motion stage z-axis interferometer, a leveling and focusing system, a motion stage, and a measuring device. The motion stage includes at least a micro-motion stage and a wafer chuck. The wafer chuck is fixed on the micro-motion stage, and the silicon wafer is adsorbed on the wafer chuck.

[0036] The motion stage z-axis interferometer, the leveling and focusing system, and the micro-motion stage are all communicatively connected to the measuring equipment.

[0037] The motion stage z-axis interferometer is used to measure the height of the motion stage under the control of the measuring equipment.

[0038] The leveling and focusing system is used to measure the initial surface height of the silicon wafer under the control of the measuring equipment;

[0039] The measuring device is used to perform the steps of the lithography machine surface measurement method according to any one of the first aspects, so as to measure the actual surface shape information of the silicon wafer.

[0040] As one possible implementation, the lithography machine optical system also includes: a base plate;

[0041] The base plate is disposed on the micro-motion stage, and the base plate includes a preset flat area.

[0042] Thirdly, embodiments of this application provide a measurement device, including: a processor, a storage medium, and a bus. The storage medium stores machine-readable instructions executable by the processor. When the measurement device is running, the processor communicates with the storage medium via the bus, and the processor executes the machine-readable instructions to perform the steps of the lithography machine surface measurement method as described in any of the first aspects above.

[0043] Fourthly, embodiments of this application provide a computer-readable storage medium storing a computer program, which, when executed by a processor, performs the steps of the lithography machine surface measurement method as described in any of the first aspects above.

[0044] According to the lithography machine surface measurement and lithography machine optical system of the embodiments of this application, the heights of multiple motion stages measured by the motion stage z-interferometer at a preset frequency and the initial surface height of the silicon wafer measured by the leveling and focusing system at a preset frequency are obtained. When the measurement error sources are consistent, the measurement height of each spot in each measurement cycle is compensated based on the motion stage height of each measurement cycle to obtain the compensated height of each spot in each measurement cycle. Based on the compensated height of each spot in each measurement cycle, the target height of each spot is obtained. The target heights of all spots are fitted to determine the actual surface shape information of the silicon wafer. According to the embodiments of this application, the measurement data output by the motion stage z-interferometer and the leveling and focusing system are both within a preset frequency. This preset frequency is less than or equal to a preset threshold, which limits the common effective signal range of the motion stage z-interferometer and the leveling and focusing system. In the presence of unavoidable low-frequency operating environments, vibration errors caused by some components in the lithography machine optical system can be avoided. Based on this, error compensation is performed on the silicon wafer measurement values ​​based on the motion stage data, thereby removing the interference components caused by the vibration of the motion stage, improving the authenticity of the silicon wafer surface height measurement, and combining the data from multiple measurement cycles with error compensation, effectively avoiding the influence of random errors on the final result. This not only improves the measurement accuracy of the leveling and focusing system, but also makes the final silicon wafer surface shape information more realistic and reliable, accurately reflecting the actual surface characteristics of the silicon wafer. Attached Figure Description

[0045] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This paper shows a schematic diagram of the architecture of a lithography machine optical system provided in an embodiment of this application;

[0047] Figure 2 A flowchart of a method for measuring the surface of a lithography machine according to an embodiment of this application is shown;

[0048] Figure 3 This paper illustrates the time-domain variation of a motion table during one sampling period, according to an embodiment of this application.

[0049] Figure 4 This paper illustrates the frequency domain variation of a motion stage within one sampling period, according to an embodiment of this application.

[0050] Figure 5 This paper illustrates the time-domain variation of a leveling and focusing system provided in an embodiment of this application during one sampling period.

[0051] Figure 6 This paper illustrates the frequency domain variation of a leveling and focusing system provided in an embodiment of this application within one sampling period.

[0052] Figure 7 The spectrum of a motion stage z-axis interferometer and leveling / focusing system provided in an embodiment of this application is shown in the 0~300Hz range.

[0053] Figure 8 This application provides a light spot distribution diagram according to an embodiment of the present application.

[0054] Figure 9 A flowchart illustrating a method for determining the height after compensation, as provided in an embodiment of this application, is shown.

[0055] Figure 10 This illustration shows the effect of a measurement data degradation process provided in an embodiment of this application.

[0056] Figure 11 This illustration shows the effect of another measurement data depotting process provided in an embodiment of this application.

[0057] Figure 12 A schematic diagram of the structure of a measuring device provided in an embodiment of this application is shown. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the accompanying drawings in this application are for illustrative and descriptive purposes only and are not intended to limit the scope of protection of this application. Furthermore, it should be understood that the schematic drawings are not drawn to scale. The flowcharts used in this application illustrate operations implemented according to some embodiments of this application. It should be understood that the operations in the flowcharts may not be implemented in sequence, and steps without logical contextual relationships may be reversed or implemented simultaneously. In addition, those skilled in the art, guided by the content of this application, may add one or more other operations to the flowcharts, or remove one or more operations from the flowcharts.

[0059] Furthermore, the described embodiments are merely some, not all, of the embodiments of this application. The components of the embodiments of this application described and illustrated herein can typically be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0060] It should be noted that the term "comprising" will be used in the embodiments of this application to indicate the presence of the features declared thereafter, but does not exclude the addition of other features.

[0061] Figure 1 A schematic diagram of the architecture of a lithography machine optical system provided in an embodiment of this application is shown. (Refer to...) Figure 1 As shown, the optical system of a lithography machine includes at least: a motion stage z-interferometer, a focusing and leveling system (FLS), a motion stage, and a measurement device. The motion stage includes at least a micro-stage, on which the silicon wafer is placed. The motion stage z-interferometer, focusing and leveling system, and micro-stage are all communicatively connected to the measurement device. The motion stage z-interferometer is used to measure the height of the motion stage under the control of the measurement device, and the focusing and leveling system is used to measure the initial surface height of the silicon wafer under the control of the measurement device.

[0062] Optionally, refer to Figure 1 As shown, the lithography machine's object-free measurement system also includes a base plate FM, which contains a preset flat area slightly larger than the photomask size, for example, a 2*2mm flat area. The base plate FM serves as a reference plane, and the leveling and focusing system FLS can be calibrated based on the preset flat area provided by the base plate FM.

[0063] Optionally, refer to Figure 1 As shown, the lithography machine's optical system also includes vibration dampers, a measurement frame, a base frame, a projection lens, a macro stage, a suspension device (NS), a marble slab, and an air float. The vibration dampers, located on both sides of the measurement frame, reduce the impact of external vibrations on the lithography machine's optical system, ensuring stability during measurement. The dampers absorb and attenuate vibration energy through internal damping materials or air springs, keeping the lithography machine's optical system relatively stationary during measurement. The base frame supports the bottom of the entire lithography machine's optical system, providing a stable platform and ensuring the relative positions of all components remain fixed. The projection lens focuses the light emitted by the leveling and focusing system (FLS) onto the silicon wafer surface, forming a bright and clear spot. The macro stage, located below the micro stage, is used to move the silicon wafer over a wide range, bringing it into the measurement area. The marble slab, located below the macro stage, provides a stable support platform. The air float, located at the bottom layer, further reduces the impact of vibrations on the lithography machine's optical system. Based on suspension technology, the air float and the suspension device (NS) suspend the entire lithography machine's optical system, thus isolating it from ground vibrations.

[0064] Based on this, the lithography machine optical system provided in this application achieves high-precision measurement of silicon wafers through the coordinated operation of multiple components. Each component in the lithography machine optical system has a specific function and working principle, which together ensure the stability and accuracy of the object surface measurement process.

[0065] The following is in conjunction with the above. Figure 1 The contents described in the optical system of the lithography machine shown herein will be explained in detail to illustrate the lithography machine surface measurement method provided in the embodiments of this application.

[0066] Figure 2 The diagram illustrates a flowchart of a lithography machine surface measurement method according to an embodiment of this application. The main body executing this method is... Figure 1 The measurement equipment in the optical system of the lithography machine shown. (Refer to...) Figure 2 As shown, the method specifically includes the following steps:

[0067] S201. Obtain the heights of multiple motion stages measured by the z-axis interferometer of the motion stage at a preset frequency, and obtain the initial surface height of the silicon wafer measured by the leveling and focusing system at a preset frequency.

[0068] Optionally, a set of measurement data can be acquired using the maximum sampling frequency of the motion stage z-interferometer (e.g., f = 5000 Hz), and Fourier fast transform and spectral analysis can be performed. However, according to the Nexus theorem, only signals within the range of f = fs / 2 are valid signals sampled, meaning the effective high-frequency signal spectral range that the motion stage z-interferometer can acquire is [0, 2500] Hz. (Refer to...) Figure 3The diagram shows the time-domain variation of the motion stage over one sampling period, and... Figure 4 The frequency domain variation diagram of the motion stage within one sampling period is shown. By extracting the height information of the motion stage's z-axis interferometer within one sampling period (e.g., 0.16s), performing potential reduction processing, and conducting spectral analysis, it can be determined that the frequencies with larger amplitudes are mainly in the range of 0~300Hz. Figure 3 The horizontal axis represents time, and the vertical axis represents the height information acquired by the interferometer in the z-direction of the motion stage. Figure 4 The horizontal axis represents frequency, and the vertical axis represents amplitude.

[0069] Optionally, the maximum sampling frequency supported by the leveling and focusing system is 625Hz. However, due to factors such as the size of the measurement spot, sampling frequency, and exposure scanning speed, the bandwidth that the leveling and focusing system can sense is limited. Therefore, by acquiring the measured height values ​​of five spots of the leveling and focusing system within one sampling period (e.g., 0.16s) and performing voltage reduction processing, the specific details can be found in [reference needed]. Figure 5 The diagram shows the time-domain variation of the leveling and focusing system over one sampling period, and... Figure 6 The frequency domain variation diagram of the leveling and focusing system shown in the figure within one sampling period shows that the effective signal frequency range of the leveling and focusing system is [0, 316] Hz.

[0070] In other words, although the sampling frequencies of the motion stage z-interferometer and the leveling and focusing system are different, spectral analysis reveals that in the measurement data of the motion stage z-interferometer, signals with larger amplitudes are concentrated in the 0~300Hz region, while the leveling and focusing system, although its maximum effective range supports 316Hz, mainly operates in the low-frequency band of 0~300Hz. (See details...) Figure 7 The spectrum diagrams of the motion stage z-interferometer and the leveling and focusing system shown are within the 0~300Hz frequency range. Clearly, there is a certain consistency between the two within this range. Therefore, this application limits the preset sampling frequencies of both the motion stage z-interferometer and the leveling and focusing system to the 0~300Hz range. That is, both the motion stage z-interferometer and the leveling and focusing system measure the motion stage height and the initial surface height of the silicon wafer within a common effective sensing frequency range where the preset frequency is less than or equal to a preset threshold (300Hz). Figure 7 The horizontal axis represents frequency, and the vertical axis represents amplitude. The red line fls represents the spectral distribution of the leveling and focusing system in the range of 0~300Hz, and the blue line ws represents the spectral distribution of the motion stage z-axis interferometer in the range of 0~300Hz.

[0071] Optionally, the initial object surface height includes: the measurement height of multiple light spots, and the distribution of the multiple light spots can be referred to... Figure 8As shown in the diagram. Here, L represents half the distance between spot 2 and spot 3. d represents the distance between spot 3 and spot 1. It should be understood that the distances between spot 2 and spot 1, spot 4 and spot 1, and spot 5 and spot 1 are all d.

[0072] S202. Based on the height of the motion table in each measurement cycle, error compensation is performed on the measurement height of each light spot in each measurement cycle to obtain the compensated height of each light spot in each measurement cycle.

[0073] Optionally, since the motion stage itself vibrates, it will affect the leveling and focusing system's measurement of the silicon wafer. Therefore, the height of the motion stage measured by the z-axis interferometer of the motion stage is used to correct the initial surface height of the silicon wafer measured by the leveling and focusing system, so as to compensate for the error of the initial surface height of the silicon wafer and finally obtain the actual surface shape information of the silicon wafer after removing the influence of the motion stage.

[0074] Optionally, for each measurement cycle, the height of the motion stage measured by the z-axis interferometer in that measurement cycle, specifically the z-axis height of the motion stage, is used to compensate for errors in the measured height of each light spot on the silicon wafer measured by the leveling and focusing system in that measurement cycle, thus obtaining the compensated height of each light spot in that cycle. Multiple measurements can eliminate random errors in the measurement process.

[0075] S203. Based on the compensated height of each light spot in each measurement round, the target height of each light spot is obtained.

[0076] Optionally, after error compensation, each light spot has a compensated height in different measurement rounds. Therefore, the target height best representing the position of each light spot can be determined based on the compensated height of each light spot in each measurement round. Specifically, as shown in formula (1), the target height of each light spot can be determined by taking the average value:

[0077] (1)

[0078] in, Indicates a light spot. Indicates the first The target height of the light spot Indicates the measurement round. , Indicates the first The first measurement round The compensated height of a light spot represents the stable height of the silicon wafer surface relative to the ideal focal plane of the lithography machine's optical system.

[0079] S204. Fit the target height of all light spots to determine the actual surface shape information of the silicon wafer.

[0080] Optionally, the actual surface shape information of the silicon wafer includes focal length information and tilt information. Based on the target height of each light spot, a plane fitting is performed based on the target height of all light spots to reconstruct the surface shape of the entire silicon wafer. Specifically, the least squares method can be used to fit the plane, and the actual surface shape information of the silicon wafer is determined by solving the least squares solution of the fitted plane equation.

[0081] Based on this, in the lithography machine surface measurement method according to the embodiments of this application, the measurement data output by the motion stage z-axis interferometer and the leveling and focusing system are both within a preset frequency range. This preset frequency is less than or equal to a preset threshold, which limits the common effective signal range of the motion stage z-axis interferometer and the leveling and focusing system. In the presence of unavoidable low-frequency operating environments, vibration errors caused by some components in the lithography machine optical system can be avoided. On this basis, error compensation is performed on the silicon wafer measurement values ​​based on the motion stage data, thereby removing the interference components caused by motion stage vibration, improving the accuracy of silicon wafer surface height measurement, and combining data from multiple measurement cycles with error compensation, effectively avoiding the influence of random errors on the final result. This not only improves the measurement accuracy of the leveling and focusing system, but also makes the final silicon wafer surface shape information more realistic and reliable, accurately reflecting the actual surface characteristics of the silicon wafer.

[0082] Figure 9 A flowchart illustrating a method for determining the height after compensation, as provided in an embodiment of this application, is shown. (Refer to...) Figure 9 As shown, step S202 above performs error compensation on the measurement height of each light spot in each measurement round based on the height of the motion table in each measurement round, to obtain the compensated height of each light spot in each measurement round. Specifically, it includes the following steps:

[0083] S901. Based on the current measurement round's motion table height and stable height, determine the motion table jitter height for the current measurement round.

[0084] Among them, the height of the motion stage is the measured height obtained by the z-axis interferometer of the motion stage, and the stable height of the motion stage is the height of the motion stage in a static and stable state.

[0085] Optionally, based on the mechanical structure of the lithography machine's optical system, the factors affecting the instability of the spot measurement data of the leveling and focusing system mainly include: noise caused by external environmental interference, vibration caused by the mechanical resonance of the motion stage (mainly including vibration dampers and air bearing vibration), vibration from silicon wafer adsorption, and the self-vibration of the charge-coupled device (CCD sensor). The factors affecting the instability of the measurement data of the z-axis interferometer of the motion stage mainly include: CCD sensor noise, noise caused by environmental interference, and jitter caused by the mechanical resonance of the motion stage. In addition, due to external environmental influences, such as vibrations (1~3Hz) caused by staff walking and talking, and swaying of the building itself (10~100Hz), even after the vibration damper isolates these low frequencies, small-amplitude low-frequency vibrations will still exist.

[0086] In other words, the height of the motion stage measured by the z-axis interferometer includes the actual height, the vibration generated by mechanical resonance, and other vibrations (such as air buoyancy vibration, damper vibration, etc.), as shown in the following formulas (2) and (3):

[0087] (2)

[0088] in, Indicates the first The vibration generated by mechanical resonance in each measurement round Indicates the first Vibration of the shock absorber under each measurement cycle Indicates the first The air-bearing vibration under each measurement cycle.

[0089] (3)

[0090] in, Indicates the first The measured height obtained by the z-axis interferometer of the motion stage in each measurement cycle. Indicates the first The stable height of the motion platform during each measurement cycle Indicates the first The vibration generated by mechanical resonance in each measurement round Indicates the first Noise generated by the first additional cause in each measurement round.

[0091] Optionally, when the optical system of the lithography machine is running normally, the noise generated by the first additional reason is very small and can be ignored in actual calculations. Based on this, the following formula (4) can be derived from the above formulas (2) and (3):

[0092] (4)

[0093] in, Indicates the first The measured height obtained by the z-axis interferometer of the motion stage in each measurement cycle. Indicates the first The stable height of the motion platform during each measurement cycle Indicates the first The vibration height of the motion table during each measurement cycle.

[0094] Specifically, for the current measurement round, based on the above formula (4), the jitter height of the motion stage in the current measurement round can be determined by using the measurement height obtained by the z-direction interferometer of the motion stage and the stable height of the motion stage.

[0095] S902. Based on the jitter height of the motion table in the current measurement cycle, perform error compensation on the measurement height of the current spot in the current cycle to obtain the compensated height of the current spot in the current cycle.

[0096] Here, the compensated height represents the stable height of the silicon wafer surface relative to the ideal focal plane of the lithography machine's optical system.

[0097] Optionally, the initial surface height of the silicon wafer measured by the leveling and focusing system includes the actual height, the vibration of the motion stage, the mechanical vibration of the leveling and focusing system itself, and the wafer adsorption vibration, as shown in the following formula (5):

[0098] (5)

[0099] in, Indicates the first The initial object surface height (i.e., the measurement height of the light spot) under each measurement round. Indicates the first The stable height of the silicon wafer surface relative to the ideal focal plane of the lithography machine's optical system in each measurement cycle. Indicates the first The height of motion table vibration during each measurement cycle Indicates the first Each measurement cycle reduces the mechanical vibration of the leveling and focusing system itself. Indicates the first Wafer adsorption vibration under each measurement round Indicates the first Noise generated by a second additional cause in each measurement round.

[0100] Furthermore, since the frequencies of the motion stage z-axis interferometer and the leveling and focusing system are both limited to 0~300Hz after spectral analysis, the specific composition of the motion stage height measured by the motion stage z-axis interferometer and the specific composition of the initial surface height of the silicon wafer measured by the leveling and focusing system can be referred to as the following formulas (6) and (7), respectively:

[0101] (6)

[0102] in, Indicates the first The measured height obtained by the z-axis interferometer of the motion stage in each measurement cycle. Indicates the first The stable height of the motion platform during each measurement cycle Indicates the first The vibration generated by mechanical resonance in each measurement round Indicates the first Vibration of the shock absorber under each measurement cycle Indicates the first The air-bearing vibration under each measurement cycle.

[0103] (7)

[0104] in, Indicates the first The first measurement round The measured height of each light spot Indicates the first The first measurement round The compensated height of each light spot, that is, the stable height of the silicon wafer surface relative to the ideal focal plane of the lithography machine's optical system. Indicates the first The height of motion table vibration during each measurement cycle Indicates the first Wafer adsorption vibration during each measurement round.

[0105] Optionally, when the lithography machine's optical system is operating normally, the noise generated by the second additional cause is very small and can be ignored in actual calculations. Furthermore, when the wafer (silicon wafer) adsorption is stable, the wafer adsorption vibration... It will approach 0 infinitely, so it can be ignored in actual calculations. Therefore, by combining the above formulas (6) and (7), we can derive the following formula (8):

[0106] (8)

[0107] in, Indicates the first The first measurement round The measured height of each light spot Indicates the first The first measurement round The compensated height of each light spot, that is, the stable height of the silicon wafer surface relative to the ideal focal plane of the lithography machine's optical system. Indicates the first The vibration height of the motion table during each measurement cycle.

[0108] Based on this, step S902 specifically includes calculating the compensated height of the current light spot according to the formula (8) above. Optionally, taking a single light spot as an example, refer to... Figure 10 As shown, the horizontal axis represents time, and the vertical axis represents the depletion value. The depletion value of the leveling and focusing system is taken from 100 measurement cycles within one sampling period (0.16s). Figure 10 (as shown by the orange curve in FLS) and the depletion value of the motion stage z-axis interferometer (as shown by...) Figure 10 As shown by the blue curve ws), the compensated leveling and focusing data calculated using the method provided in this application is more stable. Furthermore, referring to... Figure 11 As shown, the horizontal axis represents time, the vertical axis represents height, the red curve `fls` represents the original measurement value of the leveling and focusing system before compensation, and the blue curve `fls new` represents the processed value of the leveling and focusing system after compensation. The accuracy of the leveling and focusing system can be calculated from three times the standard deviation of multiple measurements. Figure 11 By calculating the two sets of data corresponding to the two curves, it can be found that the accuracy of the leveling and focusing system has decreased from 60.2nm to 46.3nm.

[0109] Therefore, for applications requiring high precision in silicon wafer surface morphology measurement in semiconductor manufacturing, where vibration of the motion stage introduces additional errors, this application effectively eliminates systematic errors caused by motion stage instability by real-time monitoring of changes in the stage height and compensating for these changes to adjust the measurement results. Furthermore, combining multiple measurements reduces the impact of random errors on the final result.

[0110] As one possible implementation, step S204 above performs fitting processing on the target height of all light spots to determine the actual surface shape information of the silicon wafer, including: using the least squares method to fit the target height of multiple light spots to determine the actual surface shape information of the silicon wafer within the light spot range of the leveling and focusing system.

[0111] Optionally, the target height of the light spot includes: the height of the light spot on the silicon wafer surface. coordinate, Coordinates and coordinate positions Silicon wafer height at the location By considering the target height of multiple light spots, the surface morphology of the silicon wafer within the exposure field of view is regarded as a plane, and the plane is fitted using the least squares method. The corresponding plane equation is shown in the following formula (9):

[0112] (9)

[0113] in, Indicates the coordinate position The height of the silicon wafer at that location, Indicates the first parameter. Indicates the second parameter. Indicates the third parameter. This represents the x-coordinate of the light spot on the silicon wafer surface. This represents the vertical coordinate of the light spot on the silicon wafer surface.

[0114] Optionally, based on the above formula (9), the light spots on the silicon wafer surface are... coordinate, Coordinates and coordinate positions Silicon wafer height at the location Input the above formula (9) into the plane fitting and solve for the least squares solution. Specifically, the first parameter It can be determined using the following formula (10):

[0115] (10)

[0116] in, Indicates the first parameter. Indicates the coordinate position The silicon wafer height at that location, where L represents half the distance between the two edge light spots (see details). Figure 8 (The annotation for L in the text).

[0117] For example, the first parameter is obtained by solving the above formula (10). The first parameter It can represent the average height of the exposure field of view, or it can be used as focal length information in the actual surface shape information of the silicon wafer.

[0118] Furthermore, when the leveling and focusing accuracy is... Figure 8 The ratio of the maximum horizontal or vertical distance of the area formed by the five light spots shown is greater than and hour( By taking RX or RY (where RX and RY represent the tilt information in the actual surface shape information of the silicon wafer), we can obtain that RX equals the third parameter C and RY equals the second parameter B. Thus, by using the least squares method to fit and solve for the first parameter A, the second parameter B, and the third parameter C, we can obtain the actual surface shape information of the silicon wafer, including the focal length information Z, and the tilt information RX and RY.

[0119] It should be noted that in the OXYZ coordinate system of the leveling and focusing system, O represents the origin, the Z-axis coincides with the optical axis of the projection lens, the Y-axis is the scanning direction of the lithography machine, and the X-plane and Y-plane coincide with the zero plane and focal plane of the leveling and focusing system, respectively. The entire OXYZ coordinate system conforms to the right-hand rule. Based on this, the focal length information Z represents the height from the focal plane, the tilt information RX represents the rotation angle around the X-axis, and RY represents the rotation angle around the Y-axis.

[0120] Based on this, this application compensates for the jitter of the motion stage on the measurement data of the leveling and focusing system, so that the RX, RY and Z values ​​returned by the leveling and focusing system can more realistically describe the silicon wafer surface.

[0121] As one possible implementation, before obtaining the initial surface height of the silicon wafer measured by the leveling and focusing system at the preset frequency, the method further includes: controlling the leveling and focusing system to emit multiple light spots onto the base plate, and performing a plane consistency detection on the multiple light spots emitted onto the base plate; if the plane consistency detection fails, adjusting the zero plane of the leveling and focusing system.

[0122] Optionally, to ensure the accuracy and consistency of the measurement results output by the leveling and focusing system, it is necessary to ensure that the zero plane of the leveling and focusing system itself coincides with the ideal focal plane of the lithography machine's optical system, and whether the difference in light spots meets the standard. That is, to perform self-checks or calibrations on the leveling and focusing system to ensure that the measurement reference of the leveling and focusing system is accurate.

[0123] Optionally, combined Figure 1 The description of the optical system of the lithography machine states that a fixed base plate FM is set on the micro-motion stage. The surface of the base plate FM is a film surface with high reflectivity and very flat. By controlling the leveling and focusing system, multiple light spots are emitted to the base plate FM, and one light spot is used to scan the base plate FM to find a preset flat area on the base plate FM. The preset flat area is slightly larger than the size of the light spot (the preset flat area is, for example, 2*2mm).

[0124] Optionally, the above steps for performing planar consistency detection on multiple light spots emitted onto the base plate specifically include:

[0125] Step A: Select one spot from the multiple spots in the leveling and focusing system as the effective spot.

[0126] For example, continue to refer to Figure 8 As shown, with Figure 8 Taking the five light spots shown as 1, 2, 3, 4 and 5 as examples, one of the light spots 1, 2, 3, 4 and 5 is selected as the effective light spot in sequence.

[0127] Step B: Move the micro-motion stage to move the center position of the preset flat area in the base plate to the effective light spot.

[0128] For example, taking spot 1 as the effective spot, the micro-motion stage is moved to move the center position of the preset flat area to the position where spot 1 is located, so as to perform single-point height measurement on spot 1.

[0129] Step C: Obtain the single-point height value obtained by the leveling and focusing system measuring the single-point height of the effective light spot.

[0130] For example, based on moving the center position of the preset flat area to the effective light spot, the leveling and focusing system can measure and output the height value of the current effective light spot. Based on the communication connection between the measuring device and the leveling and focusing system, the measuring device can directly obtain the single-point height value obtained by the leveling and focusing system from the single-point height measurement of the effective light spot.

[0131] Step D: Repeat steps A-C above to obtain the single-point height value of each light spot.

[0132] For example, continue to refer to Figure 8 As shown, for Figure 8 For each light spot shown, repeat steps A-C above to obtain the single-point height values ​​of the five light spots, which are denoted as h1, h2, h3, h4, and h5 respectively.

[0133] Step E: Determine the height difference value of each light spot relative to the center position based on the single-point height value of each light spot. If the height difference value is greater than a preset threshold, adjust the zero plane of the leveling and focusing system.

[0134] For example, the center position is the origin of the coordinate system of the leveling and focusing system, and a preset threshold is used to indicate the measurement accuracy, for example, 150 nm. Continue to refer to... Figure 8 As shown, based on the single-point height values ​​h1, h2, h3, h4, and h5 of five light spots (spot 1, spot 2, spot 3, spot 4, and spot 5), the height difference value of each light spot relative to the center position is calculated. If the height difference value is greater than a preset threshold, the zero plane of the leveling and focusing system is adjusted. If the measurement accuracy is still not met after adjusting the zero plane, the five linear CCD sensors of the leveling and focusing system need to be adjusted to recalibrate the leveling and focusing system.

[0135] Furthermore, after obtaining the height difference values ​​of each light spot relative to the center position, the difference between the maximum and minimum values ​​of the sum of the height difference values ​​of each light spot can be calculated. If the difference is greater than a preset threshold, the zero plane of the leveling and focusing system is also adjusted.

[0136] Based on this, this application performs consistency detection on multiple light spots. When the detection finds that the heights of multiple light spots are inconsistent, it indicates that the zero plane of the leveling and focusing system is not parallel or aligned with the base plate. In this case, it is necessary to adjust the zero plane of the leveling and focusing system to recalibrate the leveling and focusing system to ensure that all height values ​​measured by the leveling and focusing system are relative to a unified and accurate reference plane.

[0137] This application embodiment also provides a measuring device 1200, such as... Figure 12 The diagram shown is a structural schematic of a measurement device 1200 provided in an embodiment of this application. It includes a processor 1201 and a memory 1202, and optionally, a bus 1203. The memory 1202 stores machine-readable instructions executable by the processor 1201. When the measurement device 1200 is running, the processor 1201 and the memory 1202 communicate via the bus 1203. When the machine-readable instructions are executed by the processor 1201, they perform the steps of any of the above-mentioned lithography machine surface measurement methods.

[0138] This application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, performs the steps of any of the above-mentioned lithography machine surface measurement methods.

[0139] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems and devices described above can be referred to the corresponding processes in the method embodiments, and will not be repeated here. In the several embodiments provided in this application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. Furthermore, multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed mutual coupling or direct coupling or communication connection can be through some communication interfaces; the indirect coupling or communication connection of devices or modules can be electrical, mechanical, or other forms.

[0140] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. If the functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes: USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, optical disks, and other media capable of storing program code.

[0141] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A method for measuring the surface of a lithography machine, characterized in that, include: The system acquires multiple motion stage heights measured by a motion stage z-axis interferometer within a frequency region corresponding to a common effective signal range limited by a preset frequency less than or equal to a preset threshold, and acquires the initial surface height of the silicon wafer measured by a leveling and focusing system within a frequency region corresponding to a common effective signal range limited by the preset frequency less than or equal to a preset threshold. The preset frequency is less than or equal to the preset threshold, and the initial surface height includes the measurement height of multiple light spots. Error compensation is performed on the measurement height of each spot in each measurement cycle based on the motion stage height of each measurement cycle to obtain the compensated height of each spot in each measurement cycle. The motion stage height is the measurement height obtained by the motion stage z-axis interferometer, and the compensated height represents the stable height of the silicon wafer surface relative to the ideal focal plane of the lithography machine optical system. The target height of each light spot is obtained based on the compensated height of each light spot in each measurement round; The target height of all light spots is fitted to determine the actual surface shape information of the silicon wafer, which includes focal length information and tilt information. Before obtaining the initial surface height of the silicon wafer measured by the leveling and focusing system according to the preset frequency, the method further includes: controlling the leveling and focusing system to emit multiple light spots to the base plate, performing a plane consistency detection on the multiple light spots emitted to the base plate, and adjusting the zero plane of the leveling and focusing system if the plane consistency detection fails. The step of performing a planar consistency test on multiple light spots emitted onto the base plate, and adjusting the null plane of the leveling and focusing system if the planar consistency test fails, includes: Step A: Select one light spot from the multiple light spots of the leveling and focusing system as the effective light spot; Step B: Move the micro-motion stage to move the center position of the preset flat area in the base plate to the effective light spot; Step C: Obtain the single-point height value obtained by the leveling and focusing system measuring the single-point height of the effective light spot; Step D: Repeat steps A-C to obtain the single-point height value of each light spot; Step E: Determine the height difference value of each light spot relative to the center position based on the single-point height value of each light spot, where the center position is the origin position of the coordinate system of the leveling and focusing system. If the height difference value is greater than a preset threshold, or if the difference between the maximum and minimum values ​​of the sum of the height differences of each light spot is greater than a preset threshold, then adjust the zero plane of the leveling and focusing system.

2. The method according to claim 1, characterized in that, The method of compensating for errors in the measurement height of each light spot in each measurement cycle based on the motion table height in each measurement cycle, to obtain the compensated height of each light spot in each measurement cycle, includes: Based on the height of the motion table and the stable height of the motion table in the current measurement round, determine the motion table jitter height in the current measurement round; Based on the jitter height of the motion table in the current measurement cycle, error compensation is performed on the measurement height of the current light spot in the current cycle to obtain the compensated height of the current light spot in the current cycle.

3. The method according to claim 2, characterized in that, Determining the motion table jitter height for the current measurement round based on the motion table height and the stable height of the motion table includes: Based on formula The vibration height of the motion table is calculated. in, This indicates the measured height obtained by the z-axis interferometer of the motion stage. This indicates the stable height of the motion platform. This indicates the height of the vibration of the motion table.

4. The method according to claim 2, characterized in that, The step of performing error compensation on the measurement height of the current light spot in the current measurement round based on the jitter height of the motion table to obtain the compensated height of the current light spot in the current round includes: Based on formula The compensated height of the current light spot is calculated; in, This indicates the current measurement height of the light spot, which is the measurement height of the silicon wafer surface relative to the ideal focal plane of the lithography machine's optical system. This represents the compensated height of the current light spot, which is the stable height of the silicon wafer surface relative to the ideal focal plane of the lithography machine's optical system. This indicates the height of the vibration of the motion table.

5. The method according to claim 1, characterized in that, The process of fitting the target height of all light spots to determine the actual surface shape information of the silicon wafer includes: The target height of the multiple light spots is fitted using the least squares method to determine the actual surface shape information of the silicon wafer within the light spot range of the leveling and focusing system.

6. The method according to claim 5, characterized in that, The target height of the light spot includes: the height of the light spot on the silicon wafer surface. coordinate, Coordinates and coordinate positions Silicon wafer height at the location ; The process of fitting the target height of the multiple light spots using the least squares method to determine the actual surface shape information of the silicon wafer within the light spot range of the leveling and focusing system includes: The light spots on the silicon wafer surface coordinate, Coordinates and coordinate positions Silicon wafer height at the location Enter the formulas respectively A plane fitting is performed to obtain the least squares solution; where... Indicates the coordinate position The height of the silicon wafer at that location, Indicates the first parameter. Indicates the second parameter. Indicates the third parameter. This represents the x-coordinate of the light spot on the silicon wafer surface. This represents the ordinate of the light spot on the silicon wafer surface; The first parameter corresponding to the least squares solution is used as the focal length information, and the second and third parameters corresponding to the least squares solution are used as the tilt information.

7. An optical system for a lithography machine, characterized in that, The optical system of the lithography machine includes at least: a motion stage z-axis interferometer, a leveling and focusing system, a motion stage, and a measuring device. The motion stage includes at least a micro-stage and a wafer chuck. The wafer chuck is fixed on the micro-stage, and the silicon wafer is adsorbed on the wafer chuck. The motion stage z-axis interferometer, the leveling and focusing system, and the micro-motion stage are all communicatively connected to the measuring equipment. The motion stage z-axis interferometer is used to measure the height of the motion stage under the control of the measuring device within a frequency region corresponding to a common effective signal range with a preset frequency less than or equal to a preset threshold limit. The height of the motion stage is the measured height obtained by the motion stage z-axis interferometer. The leveling and focusing system is used to measure the initial surface height of the silicon wafer within a frequency range corresponding to a common effective signal range that is less than or equal to a preset threshold, under the control of the measuring device. The initial surface height includes the measurement height of multiple light spots, and the preset frequency is less than or equal to the preset threshold. The measuring device is used to perform the steps of the lithography machine surface measurement method according to any one of claims 1-6, so as to measure the actual surface shape information of the silicon wafer.

8. The system according to claim 7, characterized in that, The optical system of the lithography machine also includes: a base plate; The base plate is disposed on the micro-motion stage, and the base plate includes a preset flat area.

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