Exposure system and dose control method for an exposure system

Abstract

This invention provides a dose control method for an exposure system having at least two sub-exposure systems. The method includes: calculating the maximum scanning speed of each sub-exposure system based on the set exposure dose, set reference illuminance, and effective field of view width; comparing the maximum scanning speed of each sub-exposure system with the maximum scanning speed supported by the stage and selecting the lowest value as the stage's scanning speed; calculating the transmittance of the continuously variable attenuator in each sub-exposure system based on the stage's scanning speed; calculating the scanning time based on the user-specified scanning field length and the stage's scanning speed; and triggering a synchronization signal based on the scanning time to control the shutter switch of the designated exposure system for scanning exposure. This method solves the problem that lithography machines with multiple independent exposure systems cannot achieve independent exposure of a designated exposure system or exposure with different doses.

Description

Technical Field

[0001] This invention relates to the field of lithography machines, and in particular to an exposure system and a dose control method for the exposure system. Background Technology

[0002] In lithography, the precision of exposure dose control directly affects the imaging effect. Lithography machines are categorized into single-exposure systems and multi-exposure systems based on the number of exposure systems. Multi-exposure systems offer a larger field of view, effectively increasing yield. Industry-standard multi-exposure system lithography machines employ a stitched objective lens scheme, requiring synchronized image stitching dose exposure across all systems to ensure consistent exposure doses. Currently, lithography machines using multiple independent exposure systems cannot achieve independent exposure for a specific system, nor can they simultaneously perform exposures with different doses across multiple systems. Summary of the Invention

[0003] The purpose of this invention is to provide an exposure system and a dose control method for the exposure system, so as to solve the problem that a lithography machine using multiple exposure systems cannot achieve independent exposure of a specified exposure system, nor can it achieve simultaneous exposure of multiple exposure systems with different doses.

[0004] To address the aforementioned technical problems, this invention provides a dose control method for an exposure system, wherein the exposure system has at least two sub-exposure systems, including:

[0005] Set the exposure dose and reference illuminance for each sub-exposure system; the exposure dose of each sub-exposure system is independently adjustable.

[0006] The maximum scanning speed of each exposure system is calculated based on the exposure dose, reference illuminance, and effective field of view set for each exposure system.

[0007] Compare the maximum scanning speed of each sub-exposure system with the maximum scanning speed supported by the stage, and select the lowest value as the scanning speed of the stage; calculate the transmittance of the continuously variable attenuator in each sub-exposure system based on the scanning speed of the stage.

[0008] The scanning time is calculated based on the scanning field length and the scanning speed of the workpiece stage provided by the user, and the synchronization signal is triggered based on the scanning time to control the shutter switch of the designated exposure system for scanning exposure.

[0009] Optionally, the formula for calculating the transmittance of the continuously variable attenuator in the i-th sub-exposure system is:

[0010]

[0011] Where Dose[i] is the set exposure dose of the i-th sub-exposure system, Vws_scan Let I[i] be the scanning speed of the workpiece stage, I[i] be the reference illuminance of the i-th sub-exposure system, and L[i] be the reference illuminance. slit Let be the effective field of view width of the i-th sub-exposure system, where i is a positive integer.

[0012] Optionally, each sub-exposure system can pre-calibrate the deviation value of the exposure dose, where the deviation value is the equipment deviation.

[0013] Optionally, before setting the exposure dose and reference illuminance for each sub-exposure system, the light source power of the other sub-exposure systems is adjusted based on one of the sub-exposure systems to ensure that the illuminance of the multiple sub-exposure systems obtained by the energy point sensor is consistent within the set error range.

[0014] Optionally, the parameters of the energy detector of each sub-exposure system can be calibrated using the same energy point sensor to ensure that the illuminance collected by the energy detector and the energy point sensor of each sub-exposure system is consistent.

[0015] Based on the same inventive concept, the present invention also provides an exposure system, including at least two sub-exposure systems, a workpiece stage and a control system;

[0016] The control system sets the exposure dose and reference illuminance for each sub-exposure system, with the exposure dose of each sub-exposure system being independently adjustable. It calculates the maximum scanning speed of each sub-exposure system based on the set exposure dose, reference illuminance, and effective field of view width. It compares the maximum scanning speed of each sub-exposure system with the maximum scanning speed supported by the stage, selecting the lowest value as the stage's scanning speed. It calculates the transmittance of the continuously variable attenuator in each sub-exposure system based on the stage's scanning speed. It calculates the scanning time based on the user-specified scanning field length and the stage's scanning speed, and triggers a synchronization signal based on the scanning time to control the shutter switch of the designated exposure system for scanning exposure.

[0017] Optionally, the exposure system includes a light source, and each exposure system is set with an exposure dose and a reference illuminance.

[0018] Optionally, the exposure system includes a continuously variable attenuator, and the exposure dose of each exposure system is independently adjusted by calculating the transmittance of the continuously variable attenuator.

[0019] Optionally, the continuously variable attenuator includes a motor and blades, with the motor driving the blades to move in a straight line to achieve continuous change in the transmittance of the continuously variable attenuator.

[0020] Optionally, the exposure system may further include a compensation version for adjusting the illuminance uniformity of the exposure system.

[0021] In the exposure system and dose control method provided by this invention, the maximum scanning speed of each sub-exposure system is compared with the maximum scanning speed supported by the stage, and the lowest value is selected as the scanning speed of the stage. Each sub-exposure system calculates the transmittance of the continuously variable attenuator based on the scanning speed of the stage. The exposure dose of each sub-exposure system is adjusted in coordination with the transmittance of the continuously variable attenuator in each sub-exposure system to ensure consistent illumination in each sub-exposure system. Furthermore, each sub-exposure system can also pre-set the exposure dose deviation for the corresponding field of view to compensate for the inconsistency in the linewidth of the devices on the wafer after exposure. At the same time, the exposure dose in each sub-exposure system of this invention can be adjusted independently, thereby solving the problem that for lithography machines with multiple independent exposure systems, it is impossible to achieve independent exposure of a specified exposure system or to achieve simultaneous exposure of different doses by multiple exposure systems. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of an exposure system according to an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the structure of a continuously variable attenuator according to an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram showing the positional relationship between the blades of the continuously variable attenuator and the exposure field of view in an embodiment of the present invention;

[0025] Figure 4 This is a schematic diagram of the structure of the compensated version of this invention;

[0026] Figure 5 This is a flowchart of a dose control method for an exposure system according to an embodiment of the present invention;

[0027] In the picture,

[0028] 10-Exposure system; 11-Light source; 12-Shutter; 13-Continuously variable attenuator; 13a-Blade; 13b-Motor; 13c-Shaft; 14-Illumination module; 14a-Coupled unit; 14b-Light homogenizing unit; 14d-Energy detector; 14c-Relay unit; 15-Compensation plate; 15a-Through hole; 16-Objective lens; 17-Exposure field of view; 20-Stage; 21-Energy point sensor. Detailed Implementation

[0029] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a further detailed explanation of the exposure system and its dose control method. The advantages and features of the present invention will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0030] Figure 1 This is a schematic diagram of an exposure system according to an embodiment of the present invention. Figure 1 As shown, this embodiment provides an exposure system, including at least one sub-exposure system 10, a workpiece stage 20, and a control system (not shown in the figure).

[0031] The control system sets the exposure dose and reference illuminance for each sub-exposure system 10. The exposure dose of each sub-exposure system is independently adjustable. Based on the set exposure dose, set reference illuminance, and effective field of view width of each sub-exposure system, the maximum scanning speed of each sub-exposure system is calculated. The maximum scanning speed of each sub-exposure system is compared with the maximum scanning speed supported by the workpiece stage, and the lowest value is selected as the scanning speed of the workpiece stage. The transmittance of the continuously variable attenuator in each sub-exposure system is calculated based on the scanning speed of the workpiece stage. The scanning time is calculated based on the scanning field length issued by the user and the scanning speed of the workpiece stage, and the synchronization signal is triggered based on the scanning time to control the shutter switch of the designated exposure system for scanning exposure.

[0032] The workpiece stage 20 is used to carry the wafer and move the wafer.

[0033] like Figure 1 As shown, the exposure system includes a light source 11, a shutter 12, a continuously variable attenuator 13, an illumination module 14, a compensation plate 15, and an objective lens 16. The light source 11 provides a light beam and can be set with an exposure dose and a reference illuminance. The continuously variable attenuator 13 adjusts the illuminance of the exposure system; by adjusting the transmittance of the continuously variable attenuator 13, the exposure dose of each exposure system 10 can be adjusted independently. The illumination module 14 couples and homogenizes the light beam emitted by the light source to match the field of view of the objective lens 16. The compensation plate 15 adjusts the illuminance uniformity of the exposure system. The objective lens 16 projects the light beam onto the workpiece 20. The objective lens 16 may include, for example, a movable lens, through which the magnification of the objective lens is adjusted to achieve the required magnification for photolithography of the silicon wafer pattern.

[0034] Figure 2 This is a schematic diagram of the structure of a continuously variable attenuator according to an embodiment of the present invention. Figure 3 This is a schematic diagram showing the positional relationship between the blades of the continuously variable attenuator and the exposure field of view in an embodiment of the present invention. Figure 2 and Figure 3 As shown, the continuously variable attenuator 13 includes blades 13a and a motor 13b. The motor 13b is connected to a rotating shaft 13c, and the blades 13a are located on the rotating shaft 13c. The motor 13b drives the blades 13a to move linearly through the rotating shaft 13c. The transmittance of the continuously variable attenuator 13 is continuously changed by adjusting the size of the light-blocking area of ​​the blades 13a. The blades 13a move along the direction perpendicular to the exposure field of view 17 to block the exposure field of view 17, thereby adjusting the illuminance of the exposure system 10.

[0035] Figure 4 This is a structural and partial enlarged schematic diagram of the compensated version of this invention, according to an embodiment of the invention. Figure 4 As shown, the compensation plate 17 has a plurality of through holes 17a, and the uniformity of the illuminance of the exposure system is adjusted by setting the density and position of the through holes 17a. In this embodiment, an energy point sensor (ESS) 21 is used to test the uniformity of illuminance in each exposure field of view, and the compensation plate is drawn according to the uniformity distribution of illuminance in each exposure field of view. The compensation plate 17 is installed at the light outlet of the illumination module 14 and is used to adjust the uniformity of illuminance in the exposure field of view.

[0036] Continue to refer to Figure 1 The illumination module 14 includes a coupling unit 14a, a homogenizing unit 14b, a relay unit 14c, and an energy detector 14d. In this embodiment, the parameters of the energy detectors 14d of each exposure system 10 are calibrated using the same energy point sensor 21. After calibration, it is ensured that the illuminance collected by the energy detectors 14d and the energy point sensor 21 in each sub-exposure system is consistent.

[0037] In this embodiment, the coupling unit 14a couples the energy-controlled exposure beam. Through the coupling effect of the coupling unit 14a, the numerical aperture (NA) parameter of the exposure beam can be adjusted, and the fusion effect of the exposure beam can be improved to form the desired exposure beam and increase utilization. For example, through coupling, an exposure beam with a circular cross-section can be coupled into an exposure beam with a square or regular polygonal cross-section, making the exposure beam conform to the requirements of the optical path.

[0038] In this embodiment, the energy detector 14d is used to detect the illuminance of the illumination beam after being homogenized by the homogenizing unit 14b. The homogenizing unit 14b can homogenize the coupled exposure beam, thereby ensuring that the exposure beam meets the uniformity requirements. Insufficient uniformity of the exposure beam will affect the exposure accuracy. The exposure beam is fully homogenized in the homogenizing unit 14b, resulting in a uniform light spot output at the exit end face. Figure 1As shown, the homogenizing unit 14b further includes a first homogenizing rod and a second homogenizing rod connected to the first homogenizing rod. The energy detector 14d detects the illumination beam emitted from the connection point between the first and second homogenizing rods. The illumination beam can be emitted from the connection point and detected by the energy detector 14d. Only a very small portion of the illumination beam is retained (less than 0.1%, negligible impact on the energy balance of the illumination beam), thereby enabling real-time feedback of energy changes in the illumination beam within the exposure equipment. The first and second homogenizing rods can be made of quartz. Quartz can be used to create homogenizing rods with superior performance; for example, fused silica can be used as the homogenizing rod.

[0039] Figure 5 This is a flowchart of a dose control method for an exposure system according to an embodiment of the present invention. Figure 5 As shown, this embodiment provides a dose control method for an exposure system, including:

[0040] Step S10: Set the exposure dose and reference illuminance for each sub-exposure system;

[0041] Step S20: Calculate the exposure time of each sub-exposure system based on the exposure dose and the set reference illuminance set for each sub-exposure system.

[0042] Step S30: Calculate the maximum scanning speed of each sub-exposure system based on the exposure time of each sub-exposure system and the effective field of view of each sub-exposure system;

[0043] Step S40: Compare the maximum scanning speed of each sub-exposure system with the maximum scanning speed supported by the workpiece stage, and select the lowest value as the scanning speed of the workpiece stage.

[0044] Step S50: Calculate the transmittance of the continuously variable attenuator in each sub-exposure system based on the scanning speed of the workpiece stage;

[0045] Step S60: Calculate the scanning time based on the scanning field length and the scanning speed of the workpiece stage provided by the user, and trigger the synchronization signal to control the shutter switch of the specified exposure system to perform scanning exposure based on the scanning time.

[0046] In a specific embodiment, before setting the exposure dose and reference illuminance in step S10, the following steps may also be included:

[0047] Step S10a: Using one of the sub-exposure systems as a reference, adjust the light source power of the other sub-exposure systems so that the illuminance of the multiple sub-exposure systems acquired by the energy detector 14d is consistent within the set error range.

[0048] Step S10b: Use the same energy point sensor to calibrate the parameters of the energy detector of each exposure system to ensure that the illuminance collected by the energy detector and the energy point sensor of each exposure system is consistent.

[0049] In step S10, the exposure dose of each sub-exposure system is independently adjustable.

[0050] In step S20, the exposure time is calculated based on the set exposure dose and set reference illuminance for each sub-exposure system using the following formula:

[0051]

[0052] Where Dose[i] is the set exposure dose of the i-th sub-exposure system, and I[i] is the reference illuminance of the i-th sub-exposure system.

[0053] In this embodiment, since the exposure dose of each sub-exposure system is adjustable, it is necessary to calculate the exposure time of each sub-exposure system separately.

[0054] In step S30, the formula for calculating the maximum scanning speed of each exposure system based on the exposure time and effective field of view of each exposure system is as follows:

[0055]

[0056] Where, Li slit Let T[i] be the effective field of view of the i-th sub-exposure system. expo For each sub-exposure system, the exposure time is given, Dose[i] is the set exposure dose for the i-th sub-exposure system, and I[i] is the reference illuminance for the i-th sub-exposure system.

[0057] In this embodiment, each sub-exposure system calculates its maximum scanning speed based on its own exposure time and the effective field of view of the exposure system. Since the exposure dose of each sub-exposure system in this embodiment is adjustable, the maximum scanning speed of each sub-exposure system is also different and needs to be calculated separately.

[0058] In step S40, the maximum scanning speed of each exposure system is compared with the maximum scanning speed supported by the stage, and the lowest value is selected as the scanning speed of the stage. The calculation formula is as follows:

[0059] V ws_scan =Min{V max V[1] scan V[2] scan …} (3)

[0060] Among them, V maxV[1] represents the maximum scanning speed supported by the workpiece stage. scan V[2] represents the maximum scan speed of the first exposure system. scan This is the maximum scanning speed of the second exposure system.

[0061] In existing technologies, multi-exposure systems do not support the setting of different exposure parameters, and therefore only have one maximum scanning speed, without the need for comparison and selection of the minimum speed. In this embodiment, in order for the multi-exposure system to perform exposures with different exposure parameters, a step of comparing and selecting the minimum scanning speed needs to be added to simultaneously meet the performance requirements of the workpiece stage and the exposure requirements of each exposure system.

[0062] In step S50, the transmittance of the continuously variable attenuator in each sub-exposure system is calculated based on the scanning speed of the workpiece stage. The formula for calculating the transmittance of the continuously variable attenuator in the i-th sub-exposure system is as follows:

[0063]

[0064] Where Dose[i] is the set exposure dose of the i-th sub-exposure system, V ws_scan Let I[i] be the scanning speed of the workpiece stage, I[i] be the reference illuminance of the i-th sub-exposure system, and L[i] be the reference illuminance. slit Let be the effective field of view width of the i-th sub-exposure system, where i is a positive integer.

[0065] In this embodiment, each sub-exposure system can support exposure processes with different exposure doses and illuminance. Therefore, it is necessary to adjust the level of the continuously variable attenuator in each sub-exposure system according to the actual scanning speed of the workpiece stage.

[0066] In step S60, the formula for calculating the scanning time of the scanning field of each exposure system based on the length of the scanning field of each exposure system and the scanning speed of the workpiece stage is as follows:

[0067]

[0068] Among them, V ws_scan L is the scanning speed of the workpiece stage. scan The scan length assigned to the user.

[0069] In this embodiment, the exposure dose of each sub-exposure system is independently adjustable. In the exposure system, the exposure dose is affected by the exposure time and illuminance. The exposure time of each sub-exposure system is consistent, being the scan time of the scan field for each sub-exposure system. Therefore, to maintain consistent illuminance across each sub-exposure system, the exposure dose of each sub-exposure system can be adjusted by the transmittance of the continuously variable attenuator. Theoretically, consistent illuminance across each sub-exposure system would result in consistent linewidths on the silicon wafer. However, in practice, even with consistent illuminance across each sub-exposure system, the linewidths on the exposed silicon wafer remain inconsistent. In this case, the problem of inconsistent linewidths on the silicon wafer is compensated for by setting an exposure dose deviation. Therefore, in this embodiment, the exposure dose deviation value of each sub-exposure system can be pre-calibrated, and the exposure dose deviation value is the equipment deviation. The control system of the exposure system is equipped with a dose deviation setting window.

[0070] In another embodiment, an exposure system is used for a single exposure system. That is, among multiple sub-exposure systems, one sub-exposure system can be selected to operate. The user can specify a particular field of view for single-system exposure according to requirements. Unlike the dose control method for multiple sub-exposure systems, when using single-system exposure, the exposure system specified by the user participates in the negotiation of scanning speed. In other words, only the maximum scanning speed supported by the stage and the maximum scanning speed of the single exposure system are negotiated. Exposure systems not specified by the user do not participate in operation and do not respond to synchronization signals.

[0071] In summary, the exposure system and dose control method provided by this invention compare the maximum scanning speed of each sub-exposure system with the maximum scanning speed supported by the stage, selecting the lowest value as the stage scanning speed. Each sub-exposure system calculates the transmittance of the continuously variable attenuator based on the stage scanning speed. The exposure dose of each sub-exposure system is adjustable, and the exposure dose of each sub-exposure system is adjusted in conjunction with the transmittance of the continuously variable attenuator in each sub-exposure system, ensuring consistent illumination across all sub-exposure systems. Furthermore, each sub-exposure system can be pre-set with an exposure dose deviation corresponding to the field of view to compensate for inconsistencies in wafer linewidth after exposure. The exposure dose in each sub-exposure system of this invention can be independently adjusted, thereby solving the problem that for lithography machines with multiple independent exposure systems, it is impossible to achieve independent exposure of a specified exposure system or to simultaneously complete exposures with different doses by multiple exposure systems.

[0072] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to mutually. In addition, different parts between embodiments can also be combined with each other, and this invention does not limit this.

[0073] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A dose control method for an exposure system, said exposure system having at least two sub-exposure systems, characterized in that, include: Set the exposure dose and reference illuminance for each sub-exposure system; the exposure dose of each sub-exposure system is independently adjustable. The maximum scanning speed of each exposure system is calculated based on the exposure dose, reference illuminance, and effective field of view set for each exposure system. Compare the maximum scanning speed of each sub-exposure system with the maximum scanning speed supported by the stage and select the lowest value as the scanning speed of the stage. Calculate the transmittance of the continuously variable attenuator in each sub-exposure system based on the scanning speed of the stage. The scanning time is calculated based on the scanning field length and the scanning speed of the workpiece stage provided by the user, and the synchronization signal is triggered based on the scanning time to control the shutter switch of the designated exposure system for scanning exposure.

2. The dose control method for the exposure system as described in claim 1, characterized in that, The formula for calculating the transmittance of the continuously variable attenuator in the i-th sub-exposure system is: in, The exposure dose set for the i-th sub-exposure system. The scanning speed of the workpiece stage. The reference illuminance set for the i-th sub-exposure system. Let be the effective field of view width of the i-th sub-exposure system, where i is a positive integer.

3. The dose control method for the exposure system as described in claim 1, characterized in that, Each exposure system can pre-calibrate the deviation value of the exposure dose, and the deviation value of the exposure dose is the equipment deviation.

4. The dose control method for the exposure system as described in claim 1, characterized in that, Before setting the exposure dose and reference illuminance for each sub-exposure system, adjust the light source power of the other sub-exposure systems based on one of the sub-exposure systems to ensure that the illuminance of the multiple sub-exposure systems obtained by the energy point sensor is consistent within the set error range.

5. The dose control method for the exposure system as described in claim 1, characterized in that, The parameters of the energy detector of each sub-exposure system are calibrated using the same energy point sensor to ensure that the illuminance collected by the energy detector and the energy point sensor of each sub-exposure system is consistent.

6. An exposure system, characterized in that, Includes at least two separate exposure systems, a workpiece stage, and a control system; The control system sets the exposure dose and reference illuminance for each sub-exposure system, and the exposure dose of each sub-exposure system is independently adjustable. The maximum scanning speed of each sub-exposure system is calculated based on the exposure dose, reference illuminance, and effective field of view width set for each sub-exposure system. The maximum scanning speed of each sub-exposure system is compared with the maximum scanning speed supported by the stage, and the lowest value is selected as the scanning speed of the stage. The transmittance of the continuously variable attenuator in each sub-exposure system is calculated based on the scanning speed of the stage. The scanning time is calculated based on the scanning field length issued by the user and the scanning speed of the stage, and the synchronization signal is triggered based on the scanning time to control the shutter switch of the designated exposure system for scanning exposure.

7. The exposure system as described in claim 6, characterized in that, The exposure system includes a light source, and each exposure system is set with an exposure dose and a reference illuminance.

8. The exposure system as described in claim 6, characterized in that, The exposure system includes a continuously variable attenuator, and the exposure dose of each exposure system is independently adjusted by calculating the transmittance of the continuously variable attenuator.

9. The exposure system as described in claim 8, characterized in that, The continuously variable attenuator includes a motor and blades. The motor drives the blades to move in a straight line to achieve a continuous change in the transmittance of the continuously variable attenuator.

10. The exposure system as claimed in claim 6, characterized in that, The exposure system also includes a compensation plate, which is used to adjust the illuminance uniformity of the exposure system.

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