Semiconductor photoetching machine double-workpiece-stage alignment system based on single-frequency laser self-heterodyne

Abstract

The invention relates to a semiconductor photoetching machine double-workpiece stage alignment system based on single-frequency laser self-heterodyne, which is characterized in that an electromagnetic wave heterodyne technology is utilized, a single-frequency laser transmitter is used for transmitting original laser, modulated laser is obtained through intermediate frequency signal modulation, and one laser is controlled to be transmitted to each target point on a to-be-measured plane of a first workpiece stage to be reflected; after being combined with another laser emitted to the to-be-measured plane of the first workpiece table through corresponding target points on the to-be-measured plane of the second workpiece table, the laser is received by the photoelectric detector, and heterodyne frequency mixing and demodulation are performed to obtain intermediate frequency signals which are sent to the control module; the position relation between target points corresponding to the to-be-detected plane of the first workpiece table and the to-be-detected plane of the second workpiece table is obtained through analysis of the control module, posture adjustment is conducted on the positions of the target points of the workpiece tables through the electrostriction devices, and position correction between the two workpiece tables is achieved. The method is jointly applied to the correction operation of the photoetching machine, and the precision is far higher than that of the correction technology of the photoetching machine in the prior art.

Description

Technical Field

[0001] The invention relates to a semiconductor photolithography machine double workpiece stage alignment system based on single-frequency laser self-heterodyne, belonging to the technical field of semiconductor photolithography machine correction control. Background Art

[0002] The relative position measurement of the dual worktables of the lithography machine is very critical. The existing technology mainly adopts the interferometer measurement system based on the grating interferometry method to achieve it. By measuring the changes in the laser interference fringes, the displacement and angle change of the worktable in three-dimensional space are measured. When there is a position deviation between the two worktables, the optical measurement system will detect this deviation; but the measurement accuracy that can be achieved by the measurement system based on the grating interferometry method in actual application is usually 1 / 2-1 / 5 of the wavelength, and the measurement accuracy is low. In addition, the measurement system based on the grating interferometry method requires dual laser sources, and the stability requirements of the dual laser sources are high, which makes the equipment cost high and the system complexity high. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a dual-worktable alignment system for a semiconductor lithography machine based on single-frequency laser self-heterodyne. The innovative design introduces an improved optical heterodyne phase detection application to maximize the correction accuracy of the lithography machine and realize high-efficiency operation of the lithography machine.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions: the present invention designs a semiconductor lithography machine double workpiece stage alignment system based on single-frequency laser self-heterodyne, which is used to obtain the positional relationship between the planes to be measured on the two workpiece stages in the semiconductor lithography machine, including a single-frequency laser transmitter, a laser modulator, a photodetector, and a control module. The laser modulator is used to receive the original laser emitted by the single-frequency laser transmitter, and perform frequency modulation using an intermediate frequency signal to obtain a modulated laser, and retain the original laser, and further emit them separately;

[0005] The modulated laser emitted by the laser modulator is controlled to be reflected by a preset integer number N of target points on the plane to be measured of the first workpiece stage, and then combined with the original laser emitted by the laser modulator via the corresponding target points on the plane to be measured of the second workpiece stage to the plane to be measured of the first workpiece stage, and then received by the photodetector; or the original laser emitted by the laser modulator is controlled to be reflected by the N target points on the plane to be measured of the first workpiece stage, and then combined with the modulated laser emitted by the laser modulator via the corresponding target points on the plane to be measured of the second workpiece stage to the plane to be measured of the first workpiece stage, and then received by the photodetector;

[0006] The photoelectric detector performs heterodyne mixing processing and demodulation processing on the combined wave of the received N groups of original lasers and modulated lasers, obtains intermediate frequency signals corresponding to the N target points, and sends the N intermediate frequency signals to the control module; the control module performs analysis processing on the received N intermediate frequency signals, and obtains the positional relationship between the first workpiece stage to be measured plane and the second workpiece stage to be measured plane corresponding to the N target points.

[0007] As a preferred technical solution of the present invention: a half-mirror is respectively set at each target point position on the plane to be measured of the first workpiece stage, and a total reflection mirror is respectively set at each target point position on the plane to be measured of the second workpiece stage. Then, based on n∈[1, N], for the original laser and the modulated laser output by the laser modulator, the modulated laser is controlled to be reflected by the half-mirror at the nth target point position on the plane to be measured of the first workpiece stage and emitted to the photodetector; at the same time, the original laser is controlled to be reflected by the half-mirror at the nth target point position on the plane to be measured of the first workpiece stage, and reflected by the total reflection mirror corresponding to the nth target point position on the plane to be measured of the second workpiece stage, and then transmitted to the half-mirror corresponding to the nth target point position on the plane to be measured of the first workpiece stage, and combined with the modulated laser reflected by the half-mirror at the nth target point position on the plane to be measured of the first workpiece stage, and emitted to the photodetector, which is received by the photodetector, and the positional relationship between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage corresponding to the N target points is obtained through the control module.

[0008] As a preferred technical solution of the present invention: a first reflector and a second reflector are respectively set at each target point position on the plane to be measured of the first workpiece stage, and a total reflector is respectively set at each target point position on the plane to be measured of the second workpiece stage. Then, based on n∈[1, N], for the original laser and the modulated laser output by the laser modulator, the modulated laser is controlled to be directed to the first reflector at the nth target point position on the plane to be measured of the first workpiece stage to be reflected toward the photodetector; at the same time, the original laser is controlled to be reflected by the second reflector at the nth target point position on the plane to be measured of the first workpiece stage, and to be directed to the total reflector corresponding to the nth target point position on the plane to be measured of the second workpiece stage to be reflected toward the photodetector; then the modulated laser directed to the photodetector is combined with the original laser and received by the photodetector, and the positional relationship between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage corresponding to the N target points is obtained through the control module.

[0009] As a preferred technical solution of the present invention: a first half-mirror and a second half-mirror are respectively set at each target point position on the plane to be measured of the first workpiece stage, and a reflector is respectively set at each target point position on the plane to be measured of the second workpiece stage. Then, based on n∈[1, N], for the original laser and the modulated laser output by the laser modulator, the modulated laser is controlled to be reflected by the first half-mirror at the nth target point position on the plane to be measured of the first workpiece stage; at the same time, the original laser is controlled to be reflected by the second half-mirror at the nth target point position on the plane to be measured of the first workpiece stage, and to be reflected by the reflector corresponding to the nth target point position on the plane to be measured of the second workpiece stage, and then successively transmits the second half-mirror and the first half-mirror at the nth target point position on the plane to be measured of the first workpiece stage, and then is combined with the modulated laser reflected by the first half-mirror at the nth target point position on the plane to be measured of the first workpiece stage, and is received by the photoelectric detector. The positional relationship between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage corresponding to the N target points is obtained through the control module.

[0010] As a preferred technical solution of the present invention: based on N≥3 and n∈[1, N-1], for the original laser and the modulated laser output by the laser modulator, the modulated laser is controlled to be reflected on the first half-mirror at the nth target point position on the plane to be measured of the first workpiece stage, while the modulated laser is transmitted through the first half-mirror and is reflected on the first half-mirror at the adjacent n+1th target point position on the plane to be measured of the first workpiece stage; at the same time, the original laser is controlled to be reflected on the second half-mirror at the nth target point position on the plane to be measured of the first workpiece stage, while the original laser is transmitted through the second half-mirror and is reflected on the second half-mirror at the adjacent n+1th target point position on the plane to be measured of the first workpiece stage.

[0011] As a preferred technical solution of the present invention: it also includes at least one electrostrictive device connected to each of N target points on the plane to be measured on the first workpiece stage, and at least one electrostrictive device connected to each of N target points on the plane to be measured on the second workpiece stage. Based on n∈[1, N], each electrostrictive device connected to the nth target point is used to adjust the posture of the nth target point on the corresponding plane to be measured on the workpiece stage. Each electrostrictive device corresponding to the nth target point on the plane to be measured on each workpiece stage is connected to a control module. The control module adjusts the posture of the nth target point on the plane to be measured on the first workpiece stage according to the relationship between the first workpiece stage and the second workpiece stage. The measuring plane corresponds to the positional relationship between N target points, and the electrostrictive devices corresponding to the n-th target point on the plane to be measured of each workpiece stage are controlled respectively, and the posture of the n-th target point on the plane to be measured of the first workpiece stage is adjusted, and the posture of the n-th target point on the plane to be measured of the second workpiece stage is adjusted, so that the positional relationship between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage corresponding to the n-th target point is consistent with the positional relationship between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage corresponding to other target points, so as to achieve parallelism between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage.

[0012] As a preferred technical solution of the present invention: it also includes an intermediate frequency filter, the photodetector is connected to the control module via the intermediate frequency filter, the intermediate frequency signal obtained by demodulation of the photodetector is sent to the intermediate frequency filter, and the intermediate frequency filter performs intermediate frequency filtering processing and then sends it to the control module.

[0013] As a preferred technical solution of the present invention: it also includes a signal amplifier, the photodetector is connected to the control module via the signal amplifier, the intermediate frequency signal obtained by demodulation of the photodetector is sent to the signal amplifier, and the signal amplifier performs signal amplification processing and then sends it to the control module.

[0014] As a preferred technical solution of the present invention: the first worktable is a mask worktable, and the second worktable is a wafer worktable; or the first worktable is a wafer worktable, and the second worktable is a mask worktable; the first worktable and the second worktable are used for multiple exposure overlay.

[0015] The semiconductor lithography machine dual worktable alignment system based on single-frequency laser self-heterodyne of the present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0016] (1) The semiconductor photolithography machine dual worktable alignment system based on single-frequency laser self-heterodyne designed by the present invention utilizes electromagnetic wave heterodyne technology, uses a single-frequency laser transmitter to emit original laser, and uses a laser modulator to modulate the original laser with an intermediate frequency signal to obtain a modulated laser. For the modulated laser and the original laser, one of the lasers is controlled to be reflected at each target point on the plane to be measured of the first worktable, and then combined with another laser that is emitted to the plane to be measured of the first worktable via each target point on the plane to be measured of the second worktable. The intermediate frequency signal corresponding to each target point is received by a photodetector and heterodyne mixing and demodulation is performed, and the intermediate frequency signal is obtained, which is sent to a control module. The control module performs analysis and processing to obtain the position relationship between the plane to be measured of the first worktable and the plane to be measured of the second worktable corresponding to each target point, and further uses an electrostrictive device to adjust the position of each target point of the worktable to achieve position correction between the two worktables. The scheme is designed from the two aspects of detection optical path and attitude adjustment, and is jointly applied to the correction operation of the photolithography machine, with an accuracy far exceeding the accuracy of the existing correction technology of the photolithography machine.

[0017] (2) The dual-workstage alignment system for a semiconductor lithography machine based on single-frequency laser self-heterodyne designed by the present invention utilizes electromagnetic wave heterodyne technology and the characteristic that the phase information carried by the intermediate frequency signal obtained by demodulation after self-heterodyne mixing is the same as the original laser phase information, that is, the characteristic that the information remains unchanged after frequency conversion. The relative positions between the target points in the plane to be measured by the dual workstages are obtained by amplifying and subdividing the intermediate frequency signal after optical heterodyne, so that the measurement accuracy is less than 1 / 360 wavelength, thereby improving the measurement accuracy of the position relationship between the target points in the plane to be measured by the dual workstages, and further improving the measurement accuracy of the relative positions of the dual workstages of the lithography machine, thereby realizing precise alignment and correction of the dual workstages. In addition, the use of a single-frequency laser source can simplify the complexity of the system equipment and save costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of a first embodiment of a semiconductor lithography machine dual worktable alignment system based on single-frequency laser self-heterodyne designed by the present invention;

[0019] Figure 2 This is a schematic diagram of a second embodiment of a semiconductor lithography machine dual worktable alignment system based on single-frequency laser self-heterodyne designed by the present invention;

[0020] Figure 3 It is a schematic diagram of the third embodiment of the double worktable alignment system for a semiconductor lithography machine based on single-frequency laser self-heterodyne designed by the present invention. DETAILED DESCRIPTION

[0021] The specific implementation of the present invention is further described in detail below in conjunction with the drawings of the specification. It is obvious that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. Unless otherwise specified, the relative arrangement of the components and steps described in these embodiments, the numerical expressions and numerical values ​​do not limit the scope of the present disclosure. At the same time, it should be understood that for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The techniques, methods and devices known to ordinary technicians in the relevant fields may not be discussed in detail, but where appropriate, the techniques, methods and devices should be considered as part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar symbols and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings. Meanwhile, in the description of the present invention, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance. Therefore, the features defined as "first" or "second" may explicitly or implicitly include one or more features.

[0022] The semiconductor lithography machine dual worktable alignment system designed by the present invention is based on single-frequency laser self-heterodyne, and is used to obtain the position relationship between the planes to be measured on the two worktables in the semiconductor lithography machine. This includes first obtaining the position relationship between the planes to be measured on the two worktables, and then based on this position relationship, further correcting the positions of the two worktables relative to each other.

[0023] In practical applications, the design system specifically includes a single-frequency laser transmitter, a laser modulator, a photodetector, and a control module. The laser modulator is used to receive the frequency F emitted by the single-frequency laser transmitter. 0 The original laser is modulated by using the intermediate frequency signal to obtain a frequency of F 0 +F M The modulated laser and the retained frequency F 0 The original laser is further emitted separately; here F M F is the laser modulation frequency corresponding to the optical path difference of the actual two workpiece stages. M The corresponding phase difference information between the original laser and the modulated laser is included.

[0024] A single laser source generates original laser and modulated laser designed with the same frequency, and further links the photoelectric detector to receive the lasers on the detection optical paths corresponding to the two workpiece stages. Based on the distances between the photoelectric detector and the two workpiece stages, the single-frequency laser transmitter is controlled to emit the original laser, and then the modulated laser emitted by the laser modulator is controlled to be emitted through the optical system to a preset integer N target points on the plane to be measured of the first workpiece stage, and is reflected respectively, and is respectively combined with the original laser emitted by the laser modulator and emitted from the corresponding target points on the plane to be measured of the second workpiece stage through the optical system to the first workpiece stage to be measured plane, and then is received by the photoelectric detector; or the original laser emitted by the laser modulator is controlled to be reflected through the optical system to the N target points on the plane to be measured of the first workpiece stage, and is respectively combined with the modulated laser emitted by the laser modulator and emitted from the corresponding target points on the plane to be measured of the second workpiece stage through the optical system to the first workpiece stage to be measured plane, and then is received by the photoelectric detector.

[0025] In the application, the photoelectric detector performs heterodyne mixing processing and demodulation processing on the combined wave of the N groups of original lasers and modulated lasers received, obtains the intermediate frequency signals corresponding to the N target points, and sends the N intermediate frequency signals to the control module; the control module performs analysis processing on the received N intermediate frequency signals, obtains the position relationship between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage corresponding to the N target points, thus completing the first step in the design of the position correction of the two workpiece stages.

[0026] The above design utilizes electromagnetic wave heterodyne technology. For the original laser and the modulated laser obtained by frequency modulating the original laser of the same frequency using an intermediate frequency signal, the phase information carried by the intermediate frequency signal obtained by demodulation after heterodyne mixing of the original laser and the modulated laser is the same as the phase information of the original laser. The relative position between the target points in the plane to be measured on the dual workpiece stage is obtained by amplifying and subdividing the intermediate frequency signal after optical heterodyne, thereby realizing the accurate measurement of the position relationship between the target points in the plane to be measured on the dual workpiece stage.

[0027] Among them, the single-frequency laser transmitter is used to emit the original laser, and the frequency of the original laser can be set according to specific needs, which is not limited by the present invention; the laser modulator is designed to use the intermediate frequency signal to perform frequency modulation on the received original laser to obtain the modulated laser, and the frequency of the intermediate frequency signal used can be set according to specific needs, which is not limited by the present invention. The modulation method used when the intermediate frequency signal is used to perform frequency modulation on the original laser can be set according to specific needs, which is not limited by the present invention. For example, acousto-optic modulation (the corresponding laser modulator can be an acousto-optic modulator), electro-optic modulation (the corresponding laser modulator can be an electro-optic modulator), etc. can be used. If the frequency of the original laser emitted by the single-frequency laser transmitter is recorded as F 0 The frequency of the intermediate frequency signal used to perform frequency modulation is recorded as F M, then the laser modulator receives the original laser emitted by the single-frequency laser transmitter, and uses the intermediate frequency signal to perform frequency modulation to obtain the frequency of the modulated laser, which can be expressed as F 0 +F M .

[0028] Regarding the design of the corresponding optical system between the two workpiece tables, the optical system is used to control the modulated laser emitted by the laser modulator to be directed to the target point on the plane to be measured of the first workpiece table, and to control the original laser emitted by the laser modulator to be directed to the plane to be measured of the first workpiece table via the target point at the corresponding position on the plane to be measured of the second workpiece table, and to control the modulated laser and the original laser to be combined on the plane to be measured of the first workpiece table and then directed to the photodetector, which is received by the photodetector; in a specific feasible implementation manner, the optical system is designed to control the modulated laser emitted by the laser modulator to be directed to the target point on the plane to be measured of the first workpiece table and reflected to the photodetector, and to control the original laser emitted by the laser modulator to be directed to the corresponding target point on the plane to be measured of the first workpiece table, and reflected to the corresponding target point on the plane to be measured of the second workpiece table, and then reflected to the corresponding target point on the plane to be measured of the second workpiece table via the corresponding target point on the plane to be measured of the second workpiece table, and finally directed to the photodetector, wherein the modulated laser and the original laser directed to the plane to be measured of the first workpiece table are combined on the plane to be measured of the first workpiece table and then directed to the photodetector, which is received by the photodetector.

[0029] And the plane to be measured on the first workpiece stage and the plane to be measured on the second workpiece stage can be set according to specific needs. For example, they can be two planes in the first workpiece stage and the second workpiece stage to be measured for positional relationship measurement, or they can be two planes in the first workpiece stage and the second workpiece stage to be corrected for parallelism; the number and positions of the target points on the plane to be measured on the first workpiece stage can be set according to specific needs, and the target points at corresponding positions on the plane to be measured on the second workpiece stage are set accordingly, and the present invention is not limited thereto, wherein a target point on the plane to be measured on the first workpiece stage and a target point at corresponding positions on the plane to be measured on the second workpiece stage can be called the plane to be measured on the first workpiece stage and the plane to be measured on the second workpiece stage A set of target points on the measuring plane; for example, N is set to be greater than or equal to 3, and at least 3 of the N target points on the plane to be measured on the first workpiece stage are not on the same straight line, then a plane axiom is determined based on three points, and the positional relationship between the plane to be measured on the first workpiece stage and the plane to be measured between the second workpiece stage corresponding to the at least 3 target points can be measured, thereby measuring the parallelism between the plane to be measured on the first workpiece stage and the plane to be measured between the second workpiece stage, and then the high-precision dual workpiece stage displacement accuracy can be controlled to achieve precise control of the parallelism of the dual workpiece stages; when the first workpiece stage and the second workpiece stage are used for exposure overlay, the accuracy requirements of multi-level exposure can be met.

[0030] In practical applications, the photoelectric detector performs heterodyne mixing and demodulation on the combined wave of the received N groups of original lasers and modulated lasers to obtain the intermediate frequency signals corresponding to the N target points, and sends the demodulated N intermediate frequency signals to the control module; specifically, the photoelectric detector performs heterodyne mixing and demodulation on the combined wave of the received nth group of original lasers and modulated lasers (corresponding to the nth target point) to obtain the intermediate frequency signal corresponding to the nth target point, and the control module processes the phase difference information carried by the received nth intermediate frequency signal to obtain the intermediate frequency signal corresponding to the nth target point. The optical path difference between the modulated laser and the original laser is then processed based on the optical path difference corresponding to the nth target point to obtain the positional relationship between the first workpiece stage to be measured plane and the second workpiece stage to be measured plane corresponding to the nth target point. Therefore, the control module performs analytical processing on the received N intermediate frequency signals to obtain the positional relationship between the first workpiece stage to be measured plane and the second workpiece stage to be measured plane corresponding to the N target points; wherein n∈[1,N], optionally, in the case where the heterodyne mixer has nonlinearity, the photodetector should also have nonlinear characteristics and frequency matching.

[0031] In a feasible implementation, each target point on the plane to be measured of the first workpiece stage and each target point on the plane to be measured of the second workpiece stage are respectively provided with an optical mirror for realizing control of the laser directed toward the target point on the plane to be measured of the first workpiece stage and the corresponding target point on the plane to be measured of the second workpiece stage, so that the corresponding laser can be directed toward the photodetector along the preset optical path corresponding to the target point and then received by the photodetector (the optical mirrors provided for the target points on the plane to be measured of the first workpiece stage and the target points on the plane to be measured of the second workpiece stage are part of the optical system).

[0032] In practical applications, such as Figure 1 , Figure 2 , Figure 3 In the designs of the three embodiments, if each target point on the plane to be measured on the first workpiece stage is provided with a semi-transparent mirror, and each target point on the plane to be measured on the second workpiece stage is provided with a total reflection mirror, then Figure 1In the first embodiment shown, based on n∈[1, N], for the original laser and the modulated laser output by the laser modulator, the modulated laser is controlled to be reflected by the half-mirror at the nth target point position on the plane to be measured of the first workpiece stage and to be emitted to the photodetector; at the same time, the original laser is controlled to be reflected by the half-mirror at the nth target point position on the plane to be measured of the first workpiece stage, and to be emitted to the total reflection mirror corresponding to the nth target point position on the plane to be measured of the second workpiece stage, to be reflected after ΔL, and then to be emitted to the half-mirror corresponding to the nth target point position on the plane to be measured of the first workpiece stage for transmission, and to be combined with the modulated laser reflected by the half-mirror at the nth target point position on the plane to be measured of the first workpiece stage, and to be emitted to the photodetector, which is received by the photodetector, and the N corresponding planes to be measured of the first workpiece stage and the second workpiece stage are obtained through the control module. The positional relationship between the target points, wherein the photodetector performs heterodyne mixing and demodulation on the combined wave of the received nth group of original lasers and modulated lasers to obtain an intermediate frequency signal corresponding to the nth target point; further, the photodetector sends the demodulated nth intermediate frequency signal to the control module, and the control module can analyze and process the received nth intermediate frequency signal to obtain the positional relationship (expressed as ΔL) between the first workpiece stage to be measured plane and the second workpiece stage to be measured plane corresponding to the nth target point, and then obtain the positional relationship between the first workpiece stage to be measured plane and the second workpiece stage to be measured plane corresponding to N target points, wherein the demodulated nth intermediate frequency signal can also be displayed, for example, it can be displayed by the control module, and it can also be displayed by a device that supports signal display, and the present invention does not limit it.

[0033] In practical applications, if the first reflector and the second reflector are respectively set at each target point on the plane to be measured on the first workpiece stage, and the total reflector is respectively set at each target point on the plane to be measured on the second workpiece stage, then Figure 2 In the second embodiment shown, during the application process, the first reflector and the second reflector may be at a small distance in position. Based on n∈[1, N], for the original laser and the modulated laser output by the laser modulator, the modulated laser is controlled to be directed to the first reflector at the position of the nth target point on the plane to be measured of the first workpiece stage, and reflected to the photodetector; at the same time, the original laser is controlled to be directed to the second reflector at the position of the nth target point on the plane to be measured of the first workpiece stage, and reflected to the total reflector corresponding to the position of the nth target point on the plane to be measured of the second workpiece stage, and reflected to the photodetector; then the modulated laser directed to the photodetector is combined with the original laser and received by the photodetector, and the positional relationship between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage corresponding to the N target points is obtained through the control module.

[0034] In practical applications, if the first half-mirror and the second half-mirror are respectively set at each target point on the plane to be measured on the first workpiece stage, and the reflector is respectively set at each target point on the plane to be measured on the second workpiece stage, then Figure 3 In the third embodiment shown, based on n∈[1, N], for the original laser and the modulated laser output by the laser modulator, the modulated laser is controlled to be reflected toward the first half mirror 303 at the nth target point position on the plane to be measured of the first workpiece stage 302; at the same time, the original laser is controlled to be reflected toward the second half mirror 304 at the nth target point position on the plane to be measured of the first workpiece stage 302, and is reflected toward the reflector corresponding to the nth target point position on the plane to be measured of the second workpiece stage 301, and then successively transmits the second half mirror 304 and the first half mirror 303 at the nth target point position on the plane to be measured of the first workpiece stage 302, and then is combined with the modulated laser reflected by the first half mirror 303 at the nth target point position on the plane to be measured of the first workpiece stage 302, and is received by the photoelectric detector, and the positional relationship between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage corresponding to the N target points is obtained through the control module.

[0035] Regarding the modulated laser light incident on the target point position on the plane to be measured of the first workpiece stage 302 in the third embodiment, and the original laser light incident on the second half mirror 304, in actual application, Figure 3 As shown, based on N≥3 and n∈[1, N-1], for the original laser and the modulated laser output by the laser modulator, the modulated laser is controlled to be reflected on the first half mirror 303 at the nth target point position on the test plane of the first workpiece stage 302, while the modulated laser is transmitted through the first half mirror 303 and is reflected on the first half mirror 303 at the adjacent n+1th target point position on the test plane of the first workpiece stage 302; at the same time, the original laser is controlled to be reflected on the second half mirror 304 at the nth target point position on the test plane of the first workpiece stage 302, while the original laser is transmitted through the second half mirror 304 and is reflected on the second half mirror 304 at the adjacent n+1th target point position on the test plane of the first workpiece stage 302.

[0036] Further based on the above design, connect the three target points that are not on the same straight line, such as Figure 3As shown, for the nth target point among the three target points, the modulated laser of the first half-mirror 303 directed toward the nth target point in the plane to be measured of the first workpiece stage 302 is reflected by the first half-mirror 303 and directed toward the photodetector; the original laser of the second half-mirror 304 directed toward the nth target point in the plane to be measured of the first workpiece stage 302 (the original laser corresponding to the first target point is represented as F01 in the figure, the original laser corresponding to the second target point is represented as F02 in the figure, and the original laser corresponding to the third target point is represented as F03 in the figure) is reflected by the second half-mirror 304 The original laser beam reflected toward the target point at the corresponding position on the plane to be measured of the second workpiece stage 301 is reflected (by the reflector arranged at the target point) toward the plane to be measured of the first workpiece stage 302, that is, reflected toward the nth target point on the plane to be measured of the first workpiece stage 302, and transmitted toward the photodetector by the first half mirror 303 and the second half mirror 304 arranged at the nth target point; the modulated laser beam directed toward the plane to be measured of the first workpiece stage 302 is combined with the original laser beam and received by the photodetector.

[0037] like Figure 1 , Figure 2 , Figure 3 The detection optical path designs of the above three embodiments are respectively used to identify the positional relationship between the two workpiece stages, and then enter the second step of the design, that is, to calibrate the position of the two workpiece stages. In the application, based on Figure 1 , Figure 2 , Figure 3In the embodiments shown respectively, at least one electrostrictive device is further designed to be connected to the N target points on the plane to be measured of the first workpiece stage, and at least one electrostrictive device is further designed to be connected to the N target points on the plane to be measured of the second workpiece stage. In practical applications, the electrostrictive device is such as piezoelectric ceramics. Based on n∈[1, N], each electrostrictive device connected to the nth target point is used to adjust the position of the nth target point on the plane to be measured of the corresponding workpiece stage. Each electrostrictive device corresponding to the nth target point on the plane to be measured of each workpiece stage is connected to the control module. The control module adjusts each electrostrictive device corresponding to the nth target point on the plane to be measured of each workpiece stage according to the positional relationship between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage corresponding to the N target points. Control, adjust the posture of the nth target point on the plane to be measured of the first workpiece stage, and adjust the posture of the nth target point on the plane to be measured of the second workpiece stage, so that the positional relationship between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage corresponding to the nth target point is consistent with the positional relationship between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage corresponding to other target points, realize the parallelism between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage, and perform position correction on the two workpiece stages relative to each other. In this way, based on the axiom that three points determine a plane, the parallelism of the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage is controlled by adjusting the positional relationship between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage corresponding to each target point, so as to achieve precise control of the parallelism of the double workpiece stages. In another feasible implementation, if it is desired that the plane to be measured on the first workpiece stage and the plane to be measured on the second workpiece stage are parallel and equidistant from the target, the positions of at least three target points on the plane to be measured on the first workpiece stage and / or the second workpiece stage (not on the same straight line) can be adjusted so that the positional relationship between the plane to be measured on the first workpiece stage and the plane to be measured on the second workpiece stage corresponding to each target point indicates that they are equidistant from the target. This can achieve the goal that the plane to be measured on the first workpiece stage and the plane to be measured on the second workpiece stage are parallel and equidistant from the target, that is, accurate alignment and correction of the distance and parallelism of the plane to be measured on the first workpiece stage and the plane to be measured on the second workpiece stage can be achieved. It can be known that the device used to adjust the position of the nth target point on the plane to be measured on the workpiece stage can also be other devices that can realize position adjustment, and the present invention does not limit this. Based on Figure 1 The semiconductor lithography machine double worktable alignment system shown in Figure 1 is Figure 3, which is a schematic diagram of another semiconductor lithography machine double worktable alignment system provided by the present invention, the system includes an electrostrictive device corresponding to the nth target point on the plane to be measured on the first worktable and an electrostrictive device corresponding to the nth target point on the plane to be measured on the second worktable, and is controlled by a control module to adjust the positions of the nth target point on the plane to be measured on the first worktable and the nth target point on the plane to be measured on the second worktable; it meets the requirements of the overlay accuracy of the lithography machine, is convenient for sealing, and is resistant to vibration and other measures.

[0038] In another feasible implementation, the change in the positional relationship between the plane to be measured of the first workpiece stage and the plane to be measured between the second workpiece stage corresponding to the nth target point can also be characterized by the change in the optical path difference corresponding to the nth target point, and then the relative position between the plane to be measured of the first workpiece stage and the plane to be measured between the second workpiece stage corresponding to the nth target point can be corrected by adjusting the first workpiece stage and / or the second workpiece stage. When at least 3 of the N target points on the plane to be measured of the first workpiece stage are not on the same straight line, the relative position between the plane to be measured of the first workpiece stage and each of the at least 3 target points on the plane to be measured between the second workpiece stage can be corrected by adjusting the first workpiece stage and / or the second workpiece stage, that is, the relative position between the plane to be measured of the first workpiece stage and the plane to be measured between the second workpiece stage can be corrected to achieve the alignment and correction of the planes to be measured of the double workpiece stages.

[0039] In a feasible embodiment, in order to further improve the measurement accuracy of the position relationship between target points in the plane to be measured by the dual worktable, and thus further improve the measurement accuracy of the relative positions of the dual worktables of the lithography machine, the dual worktable alignment system for the semiconductor lithography machine provided by the present invention may also include one or more intermediate frequency filters and signal amplifiers to improve the signal accuracy of the intermediate frequency signal received by the control module, and thus improve the accuracy of the determined position relationship between target points in the plane to be measured by the dual worktable.

[0040] Regarding the positional relationship between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage corresponding to the N target points, in actual application, an intermediate frequency filter and a signal amplifier are further designed and introduced, and three structures are specifically designed, including connecting the photodetector to the control module via an intermediate frequency filter, connecting the photodetector to the control module via a signal amplifier, or connecting the photodetector to the control module via an intermediate frequency filter and a signal amplifier in sequence, wherein, for the intermediate frequency signal obtained by receiving the modulated laser and the original laser combined and performing heterodyne mixing processing and demodulation processing, the intermediate frequency filter is used to perform intermediate frequency filtering processing on the intermediate frequency signal, and the signal amplifier is used to perform signal amplification processing on the intermediate frequency signal.

[0041] Therefore, when the photoelectric detector is designed to be connected to the control module via an intermediate frequency filter, the intermediate frequency signal obtained by demodulation of the photoelectric detector is sent to the intermediate frequency filter, which performs intermediate frequency filtering and then sends it to the control module. The control module then processes to obtain the positional relationship between the plane to be measured on the first workpiece stage and the plane to be measured on the second workpiece stage corresponding to N target points.

[0042] When the photoelectric detector is designed to be connected to the control module via a signal amplifier, the intermediate frequency signal obtained by demodulation of the photoelectric detector is sent to the signal amplifier, which performs signal amplification processing and then sends it to the control module, which then processes to obtain the positional relationship between the first workpiece stage to be measured plane and the second workpiece stage to be measured plane corresponding to N target points.

[0043] When the photoelectric detector is designed to be connected to the control module via the intermediate frequency filter and the signal amplifier in sequence, the intermediate frequency signal obtained by demodulation of the photoelectric detector is sent to the intermediate frequency filter and the signal amplifier in sequence, the intermediate frequency filter performs intermediate frequency filtering processing and then sends it to the signal amplifier, and then the signal amplifier performs signal amplification processing and then sends it to the control module, and finally the control module processes to obtain the positional relationship between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage corresponding to N target points.

[0044] According to the above-mentioned various embodiments, the accuracy of the intermediate frequency signal output by the photoelectric detector is improved and amplified, thereby improving the accuracy of the position relationship between the first workpiece stage to be measured plane and the second workpiece stage to be measured plane.

[0045] The above-mentioned technical solution is aimed at the two workpiece stages that need to be positionally corrected in the lithography machine, and introduces an improved optical heterodyne phase detection application. It is based on the detection light path design to the two workpiece stages respectively, starts with a single-frequency laser source, and combines the laser modulation frequency corresponding to the optical path difference of the two workpiece stages to form the original laser and the modulated laser. The two workpiece stages are detected and measured respectively, and the control module completes the position relationship identification and position correction between the planes to be measured on the two workpiece stages through the photoelectric detector.

[0046] The above design scheme is specifically applied in the correction of semiconductor lithography machines, such as the first worktable is a mask worktable, and the second worktable is a wafer worktable; or the first worktable is a wafer worktable, and the second worktable is a mask worktable; the first worktable and the second worktable are used for multiple exposure overlay, that is, based on the interchangeability of the worktables and the high-precision measurement and control that can be achieved by this system, multiple exposure overlay can be achieved, that is, the high precision required for the overlay process can be guaranteed. It can be known that the semiconductor lithography machine dual worktable alignment system proposed by the present invention can also be used to measure and correct any dual worktable that needs to be aligned and corrected in other scenarios; it can also achieve alignment and correction between multiple worktables by aligning and correcting any dual worktable in the multiple worktables; when the position of one of the worktables in the dual worktables is controlled to remain unchanged, it can also be used to align and correct a single worktable.

[0047] The above-mentioned technical scheme is designed based on the semiconductor lithography machine double worktable alignment system of single-frequency laser self-heterodyne, which uses electromagnetic wave heterodyne technology, applies a single-frequency laser transmitter to emit original laser, and uses a laser modulator to modulate the original laser with an intermediate frequency signal to obtain a modulated laser, and for the modulated laser and the original laser, controls one of the lasers to reflect at each target point on the plane to be measured of the first worktable, and after being combined with another laser that is emitted to the plane to be measured of the first worktable via each target point on the plane to be measured of the second worktable, the photodetector receives and performs heterodyne mixing and demodulation to obtain the intermediate frequency signal corresponding to each target point, and sends it to the control module, which performs analysis and processing to obtain the position relationship between the plane to be measured of the first worktable and the plane to be measured of the second worktable corresponding to each target point, and further uses an electrostrictive device to adjust the posture of the position of each target point of the worktable to achieve position correction between the two worktables. The scheme is designed from the two aspects of detection optical path and posture adjustment, and is jointly applied to the correction operation of the lithography machine, and the accuracy far exceeds the accuracy of the existing correction technology of the lithography machine.

[0048] The design scheme utilizes electromagnetic wave heterodyne technology, and the characteristic that the phase information carried by the intermediate frequency signal obtained by demodulation after heterodyne mixing is the same as the original laser phase information, that is, the characteristic that the information remains unchanged after frequency conversion, and utilizes the dual characteristics of laser beams as particles and electromagnetic waves, and utilizes the information carried by the demodulated difference frequency output electromagnetic wave, as well as the phase information of the electromagnetic wave with the characteristic of being unchanged before the difference frequency. By describing the change in the absolute value of the optical path difference to subdivide the absolute value of the optical path change, the optical information is converted into electrical information, and thus tiny position changes can be processed simply and conveniently; coupled with the ingenious use of the axiom that three points determine the plane, the degree of parallelism of the two planes is detected, and the three points corresponding to the two planes can be accurately detected to ensure that the difference in the optical path difference is exactly equal.

[0049] Furthermore, the present invention proposes a semiconductor lithography machine dual worktable alignment system, including a single-frequency laser transmitter and using the single-frequency laser transmitter to emit the original laser. The single-frequency laser can avoid the high requirement for the stability of the dual laser source frequency that cannot be achieved, simplifying the complexity of the system equipment; when the heterodyne of the single-frequency laser beam is used, the external interference disappears due to the in-phase demodulation, forming a self-stabilizing system, and the improvement of the system's anti-interference ability can improve the measurement accuracy. Further in conjunction with self-heterodyne phase detection, a stable monitoring amount less than the nanometer-level process can be provided, while improving the measurement accuracy and reducing the requirements for the laser frequency. Even if a DUV laser (195 nanometers) is used as a laser transmitter, the actual application can achieve a control accuracy of 0.1-0.5 nanometers, and then the position relationship between the target points in the plane to be measured on the dual worktable can be accurately measured in the absence of an EUV light source (13.5 nanometers wavelength) or a high-stable frequency laser source. In conjunction with self-heterodyne phase detection, the application of a photodetector has high precision and high anti-interference ability, and has higher precision than directly measuring the interference light and dark image, and lower noise.

[0050] In the actual application of the above design scheme, the application of improved optical heterodyne (i.e., self-heterodyne) provides high-precision phase detection, which far exceeds the interference grating measurement and can achieve measurement and control below the nanometer level; and its reduced requirements on the laser frequency stability of the laser source solve the bottleneck of the lack of EUV light source, and provide a stable worktable below the nanometer level for multiple mask exposures. At the same time, the multi-point correction design provides simple and direct dual worktable plane alignment and control; in addition, the actual implementation of the design scheme uses controllable optical path difference to simplify the precision machining of the arc-shaped dual worktable, and the use of projection lithography can eliminate the process of making the photolithography plate.

[0051] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A semiconductor lithography machine dual worktable alignment system based on single-frequency laser self-heterodyne is used to obtain the positional relationship between the planes to be measured on the two worktables in the semiconductor lithography machine, characterized in that: It includes a single-frequency laser transmitter, a laser modulator, a photoelectric detector, and a control module. The laser modulator is used to receive the original laser emitted by the single-frequency laser transmitter, and perform frequency modulation using an intermediate frequency signal to obtain a modulated laser, and retain the original laser, and further emit it separately; The modulated laser emitted by the laser modulator is controlled to be reflected by a preset integer number N of target points on the plane to be measured of the first workpiece stage, and then combined with the original laser emitted by the laser modulator via the corresponding target points on the plane to be measured of the second workpiece stage to the plane to be measured of the first workpiece stage, and then received by the photodetector; or the original laser emitted by the laser modulator is controlled to be reflected by the N target points on the plane to be measured of the first workpiece stage, and then combined with the modulated laser emitted by the laser modulator via the corresponding target points on the plane to be measured of the second workpiece stage to the plane to be measured of the first workpiece stage, and then received by the photodetector; The photoelectric detector performs heterodyne mixing processing and demodulation processing on the combined wave of the received N groups of original lasers and modulated lasers, obtains intermediate frequency signals corresponding to the N target points, and sends the N intermediate frequency signals to the control module; The control module performs analytical processing on the received N intermediate frequency signals to obtain the positional relationship between the plane to be measured on the first workpiece stage and the plane to be measured on the second workpiece stage corresponding to the N target points.

2. According to claim 1, the semiconductor lithography machine dual worktable alignment system based on single-frequency laser self-heterodyne is characterized by: A half mirror is set at each target point position on the plane to be measured of the first workpiece stage, and a total reflection mirror is set at each target point position on the plane to be measured of the second workpiece stage. Based on n∈[1, N], for the original laser and the modulated laser output by the laser modulator, the modulated laser is controlled to be reflected by the half mirror at the nth target point position on the plane to be measured of the first workpiece stage and then to be emitted to the photodetector; at the same time, the original laser is controlled to be reflected by the half mirror at the nth target point position on the plane to be measured of the first workpiece stage, and then reflected by the total reflection mirror corresponding to the nth target point position on the plane to be measured of the second workpiece stage, and then transmitted to the half mirror corresponding to the nth target point position on the plane to be measured of the first workpiece stage, and combined with the modulated laser reflected by the half mirror at the nth target point position on the plane to be measured of the first workpiece stage, and emitted to the photodetector, which is received by the photodetector, and the positional relationship between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage corresponding to the N target points is obtained through the control module.

3. According to claim 1, the semiconductor lithography machine dual worktable alignment system based on single-frequency laser self-heterodyne is characterized by: A first reflector and a second reflector are respectively set at each target point position on the plane to be measured of the first workpiece stage, and a total reflector is respectively set at each target point position on the plane to be measured of the second workpiece stage. Based on n∈[1, N], for the original laser and the modulated laser output by the laser modulator, the modulated laser is controlled to be directed to the first reflector at the nth target point position on the plane to be measured of the first workpiece stage to be reflected toward the photodetector; at the same time, the original laser is controlled to be reflected from the second reflector at the nth target point position on the plane to be measured of the first workpiece stage, and then directed to the total reflector corresponding to the nth target point position on the plane to be measured of the second workpiece stage to be reflected toward the photodetector; then the modulated laser directed to the photodetector is combined with the original laser and received by the photodetector, and the positional relationship between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage corresponding to the N target points is obtained through the control module.

4. According to claim 1, the semiconductor lithography machine dual worktable alignment system based on single-frequency laser self-heterodyne is characterized by: A first half mirror and a second half mirror are respectively set at each target point position on the plane to be measured of the first workpiece stage, and a reflector is respectively set at each target point position on the plane to be measured of the second workpiece stage. Then, based on n∈[1, N], for the original laser and the modulated laser output by the laser modulator, the modulated laser is controlled to be reflected by the first half mirror at the nth target point position on the plane to be measured of the first workpiece stage; at the same time, the original laser is controlled to be reflected by the second half mirror at the nth target point position on the plane to be measured of the first workpiece stage, and to be reflected by the reflector corresponding to the nth target point position on the plane to be measured of the second workpiece stage, and then sequentially transmits the second half mirror and the first half mirror at the nth target point position on the plane to be measured of the first workpiece stage, and then is combined with the modulated laser reflected by the first half mirror at the nth target point position on the plane to be measured of the first workpiece stage, and is received by the photoelectric detector, and the positional relationship between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage corresponding to the N target points is obtained through the control module.

5. According to claim 4, the semiconductor lithography machine dual worktable alignment system based on single-frequency laser self-heterodyne is characterized by: Based on N≥3 and n∈[1, N-1], for the original laser and the modulated laser output by the laser modulator, the modulated laser is controlled to be reflected on the first half-mirror at the nth target point position on the plane to be measured of the first workpiece stage, while the modulated laser is transmitted through the first half-mirror and is reflected on the first half-mirror at the adjacent n+1th target point position on the plane to be measured of the first workpiece stage; at the same time, the original laser is controlled to be reflected on the second half-mirror at the nth target point position on the plane to be measured of the first workpiece stage, while the original laser is transmitted through the second half-mirror and is reflected on the second half-mirror at the adjacent n+1th target point position on the plane to be measured of the first workpiece stage.

6. The semiconductor lithography machine dual worktable alignment system based on single-frequency laser self-heterodyne according to any one of claims 1 to 5, characterized in that: The invention also includes at least one electrostrictive device connected to N target points on the plane to be measured on the first workpiece stage, and at least one electrostrictive device connected to N target points on the plane to be measured on the second workpiece stage. Based on n∈[1, N], each electrostrictive device connected to the nth target point is used to adjust the posture of the nth target point on the plane to be measured on the corresponding workpiece stage. Each electrostrictive device corresponding to the nth target point on the plane to be measured on each workpiece stage is connected to a control module. The control module adjusts the posture of the nth target point on the plane to be measured on the first workpiece stage and the second workpiece stage according to the N electrostrictive devices connected to the plane to be measured on the second workpiece stage. The positional relationship between the target points is determined, and the electrostrictive devices corresponding to the nth target points on the plane to be measured of each workpiece stage are controlled respectively, and the posture of the nth target point on the plane to be measured of the first workpiece stage is adjusted, and the posture of the nth target point on the plane to be measured of the second workpiece stage is adjusted, so that the positional relationship between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage corresponding to the nth target point is consistent with the positional relationship between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage corresponding to other target points, so as to achieve parallelism between the plane to be measured of the first workpiece stage and the plane to be measured of the second workpiece stage.

7. According to claim 1, the semiconductor lithography machine dual worktable alignment system based on single-frequency laser self-heterodyne is characterized by: It also includes an intermediate frequency filter. The photoelectric detector is connected to the control module via the intermediate frequency filter. The intermediate frequency signal obtained by demodulation of the photoelectric detector is sent to the intermediate frequency filter, and then the intermediate frequency filter performs intermediate frequency filtering processing and sends it to the control module.

8. The semiconductor lithography machine dual worktable alignment system based on single-frequency laser self-heterodyne according to claim 1, characterized in that: It also includes a signal amplifier, the photoelectric detector is connected to the control module via the signal amplifier, the intermediate frequency signal obtained by demodulation of the photoelectric detector is sent to the signal amplifier, and the signal amplifier performs signal amplification processing and then sends it to the control module.

9. The semiconductor lithography machine dual worktable alignment system based on single-frequency laser self-heterodyne according to claim 1, characterized in that: The first work stage is a mask work stage, and the second work stage is a wafer work stage; or the first work stage is a wafer work stage, and the second work stage is a mask work stage; the first work stage and the second work stage are used for multiple exposure overlay.

Images