WO2021219017A1 - Alignment and measurement system and method, and photoetching machine - Google Patents

Abstract

An alignment and measurement system and method, and a photoetching machine. The alignment and measurement system comprises at least three sets of off-axis detection imaging optical paths, each of which comprises: a laser light source (109) for emitting a laser beam; a telecentric lens (106) for enabling the laser beam to be incident to the surface of a mask (4) at a Littrow angle, and imaging a diffraction image on a CCD camera (107); and the CCD camera (107) being arranged above the telecentric lens (106), wherein the light beam is diffracted by a clearance measurement mark (8) on the mask (4) for imaging on the CCD camera (107), and a vertical clearance value between the mask (4) and a substrate (3) is obtained according to the information of the diffraction image; and at the same time, the light beam is diffracted by a mask alignment mark (9) and a substrate alignment mark (7) to form moiré fringes on the CCD camera (107), and a horizontal alignment deviation value of the mask (4) and the substrate (3) is obtained according to the information of the moiré fringes. The alignment and measurement system achieves both alignment and focusing and leveling, saves the space occupation rate of the photoetching machine, and improves the working efficiency of the photoetching machine.

Description

System, method and photoetching machine for alignment and measurement

This disclosure claims the priority of the Chinese patent application with application number 202010355166.0 filed on April 29, 2020, the entire content of which is incorporated into this disclosure by reference.

Technical field

The present disclosure relates to the technical field of lithography machines, and in particular to a system, method and lithography machine for alignment and measurement.

Background technique

In the production process of semiconductor chips, in order to achieve the desired accuracy indicators, it is necessary to accurately establish the relationship between the various coordinate systems of the lithography machine, so that the mask, the objective lens, and the stage can establish a unified positional relationship. Usually these devices will be equipped with one or more sets of vertical detection systems, which are used to adjust the focus and level of the tested substrate before realizing the alignment of the mask and the substrate. On the one hand, it ensures that the substrate is in the image of the mask pattern. Focal plane; on the other hand, so that when the substrate is exposed, the measured mark or feature is within the detection range of the substrate alignment system, reducing the measurement error caused by the defocus tilt. Most of the existing equipment is equipped with independent vertical and horizontal detection systems. In the working process, the vertical measurement is performed first, and the workpiece to be tested is focused and leveled, and then the workpiece is aligned. Performing in this order will inevitably take up a certain amount of production time, which will have an impact on the increase in yield; in addition, under special process conditions, it is necessary to perform focus and leveling field by field, which will consume more time.

Summary of the invention

(1) Technical problems to be solved

In response to the above problems, the present disclosure provides an alignment and measurement system, method, and lithography machine, which are used to at least partially solve the traditional measurement system's high space occupancy rate, long alignment and leveling time, and low lithography machine yield. And other technical issues.

(2) Technical solution

One aspect of the present disclosure provides an alignment and measurement system, which includes at least three sets of off-axis detection imaging optical paths, and each set of off-axis detection imaging optical paths includes: a laser light source for emitting a laser beam; a telecentric lens for The laser beam is incident on the mask surface at the Littrow angle, and the diffraction image is imaged on the CCD camera; the CCD camera is set above the telecentric lens, and the beam is imaged on the CCD camera after measuring the diffraction of the mark through the mask gap. According to the diffraction image information, the vertical gap value between the mask and the substrate is obtained; at the same time, the light beam is diffracted by the mask alignment mark and the substrate alignment mark to form moiré fringes on the CCD camera. The information obtains the horizontal alignment deviation value of the mask and the substrate.

Further, it also includes a six-degree-of-freedom lens attitude adjustment mechanism that matches the off-axis detection and imaging optical path, and the off-axis detection and imaging optical path is fixed on the six-degree-of-freedom lens attitude adjustment mechanism.

Further, the six-degree-of-freedom lens attitude adjustment mechanism includes: X/Y-axis translation stage; Rz-axis rotation stage, which is installed on the X/Y-axis translation stage; tilt adapter plate, which is installed on the Rz-axis rotation stage, including An inclined plane; Z-axis translation stage, which is installed on the inclined plane of the inclined adapter plate; Rx/Ry rotary stage, which is installed on the Z-axis translation stage.

Further, the six-degree-of-freedom lens posture adjustment mechanism is used to adjust the posture of the off-axis detection imaging optical path in the six-degree-of-freedom direction, and adjust the incident position and angle of the light beam.

Further, the six-degree-of-freedom lens attitude adjustment mechanism further includes a lens holder, which is installed on the Rx/Ry rotating table and used to maintain the stability of the telecentric lens and the CCD camera.

Further, the off-axis detection imaging optical path further includes: a crystal oscillator module, which is used to eliminate the coherence of the laser.

Further, the light beam emitted from the off-axis detection imaging optical path obliquely irradiates the surface of the mask without affecting the exposure of the substrate.

Further, the mask gap measurement mark is composed of two groups of chirped gratings with opposite phases, the mask alignment mark is a periodic grating alignment mark, and the substrate alignment mark is a periodic grating reflection alignment mark.

Another aspect of the present disclosure provides a method of alignment and measurement, which includes: a CCD camera collects a diffraction image of a light beam measuring a mark in a mask gap, and obtains the vertical gap value between the mask and the substrate according to the diffraction image information; at the same time; The CCD camera collects the moiré fringe formed by the diffraction of the beam on the mask alignment mark and the substrate alignment mark, and obtains the horizontal alignment deviation value of the mask and the substrate according to the information of the moiré fringe; according to the vertical gap value Adjust the position of the substrate with the horizontal alignment deviation value, and realize the alignment of the mask and the substrate.

Further, before the CCD camera collects the image, it further includes: a six-degree-of-freedom lens attitude adjustment mechanism adjusts the imaging optical path of the CCD camera, so that the mask gap measurement mark and the mask alignment mark are located in the central area of the imaging optical path at the same time.

Another aspect of the present disclosure provides a lithography machine, which includes a mask and a workpiece table, and also includes the aforementioned alignment and measurement system.

Another aspect of the present disclosure provides a measurement system that takes into account both focusing and leveling and precision alignment. The measurement system is set on a substrate and a mask. The measurement system that takes care of both alignment and focus and leveling includes three or more groups. The six-degree-of-freedom lens attitude adjustment mechanism and off-axis detection imaging optical path, the off-axis imaging optical path and the mask normal direction are incident on the surface of the mask at a Litro angle, one of a set of measurement systems that takes into account alignment and focusing and leveling The six-degree-of-freedom lens attitude adjustment mechanism and off-axis detection imaging optical path include X/Y-axis translation stage (100), Tz-axis rotation stage (101), tilt adapter plate (102), Z-axis translation stage (103), Rx/ Ry rotating stage (104), lens holder (105), telecentric lens (106), CCD (107), crystal oscillator module (108) and alignment laser light source (109), of which the Tz axis rotating stage (101) ) Is installed on the X/Y axis translation stage (100), the tilt adapter plate (102) is installed on the Tz axis rotation stage (101), and the Z axis translation stage (103) is installed on the tilt adapter plate (102), The Rx/Ry rotating stage (104) is installed on the Z-axis translation stage (103), the lens mounting plate (105) is installed on the Rx/Ry rotating stage (104), and the telecentric lens (106) is connected and clamped with the CCD (107) On the lens holder (105), the light source collimation module is installed on the illumination light source inlet of the telecentric lens.

Further, the off-axis imaging optical path includes a laser light source module, a laser decoherence module, a light source collimating lens, a telecentric lens with a light guide device, and a CCD camera sequentially arranged along the beam propagation direction. The light beam emitted by the laser light source module is oscillated by a crystal. After being collimated by the collimator and the collimator lens, it is imported into the telecentric lens, and then irradiated to the chirped grating pattern area of the mask at the designed gap measurement angle. The telecentric lens images the diffraction pattern of the chirped grating onto the CCD, and passes Perform frequency + phase analysis on the diffraction image to achieve vertical nanometer-scale online gap measurement.

Further, the off-axis imaging optical path includes a laser light source module, a laser decoherence module, a light source collimating lens, a telecentric lens with a light source lead-in interface, and a CCD camera arranged in sequence along the beam propagation direction. The light beam emitted by the laser light source module is oscillated by a crystal. The device is decoherent and collimated by the collimator lens and then poured into the telecentric lens, and then irradiated to the alignment pattern area of the mask at the designed alignment measurement angle. The alignment measurement angle is equal to the gap measurement angle, and the beam passes through the mask. The upper periodic grating is diffracted and irradiated to the alignment mark area of the substrate. After diffraction by the checkerboard grating with a certain difference between the period of the substrate and the mask grating, it returns to the telecentric lens according to the original optical path, and the telecentric lens will align the image The image is imaged on a CCD camera, and by analyzing the phase information of the alignment moiré fringe, the horizontal nanometer-level online alignment deviation detection is realized.

Further, a chirped grating calibration mark and a periodic grating alignment mark are provided on the mask.

Furthermore, a periodic grating reflection alignment mark is provided on the substrate.

Another aspect of the present disclosure provides a measurement method that takes into account both focusing and leveling and precision alignment. The aforementioned measurement system that takes care of both alignment and focus and leveling includes the following steps: Step 1: Adjustment by a six-degree-of-freedom motion platform The imaging optical path of the telecentric lens makes the chirped grating mark and the alignment mark on the mask exactly in the center area of the imaging optical path at the same time; Step 2: Adjust the CCD lens to focus, collect the diffraction image of the chirped grating, and calculate the substrate to be tested The vertical gap value with the lower surface of the mask; at the same time, the moiré pattern formed by diffraction of the mask alignment mark and the substrate alignment mark is collected, and the horizontal alignment deviation value of the mask and the substrate to be tested is calculated ; Step 3: Feedback the vertical gap value to the substrate control system to drive the workpiece table to complete the position adjustment of the substrate to be tested; Step 4: Feedback the horizontal alignment deviation value to the substrate control system to drive the workpiece table, The position adjustment of the substrate to be tested is completed, and the alignment operation between the mask and the substrate is realized.

Another aspect of the present disclosure provides a lithography machine, which includes a mask and a workpiece table. The lithography machine also includes the aforementioned measurement system that takes into account both alignment and focusing and leveling.

(3) Beneficial effects

The system, method and photoetching machine for alignment and measurement provided by the embodiments of the present disclosure are formed by simultaneously collecting the diffraction image formed by the chirped grating on the mask and the diffraction of the mask alignment mark and the substrate alignment mark Moiré fringe, the vertical gap value and horizontal alignment deviation value of the mask and the substrate can be obtained at the same time. That is, the same set of detection systems can not only realize the horizontal alignment deviation measurement in the photolithography process, but also realize the vertical alignment deviation value. The measurement of the gap value in the direction greatly reduces the space requirement of the whole machine, and also improves the work efficiency of the detection and alignment process, and at the same time does not affect the exposure process of the graphic area.

Description of the drawings

Fig. 1 schematically shows a structural diagram of the entire structure of an alignment and measurement system according to an embodiment of the present disclosure;

Fig. 2 schematically shows a top view of the entire structure of the alignment and measurement system according to an embodiment of the present disclosure;

Fig. 3 schematically shows a structural diagram of an alignment and measurement system according to an embodiment of the present disclosure;

4 schematically shows a schematic diagram of the optical path for measuring and detecting the gap between the mask and the substrate and the optical path for detecting the alignment deviation according to an embodiment of the present disclosure;

Fig. 5 schematically shows a schematic diagram of a mask gap measurement mark according to an embodiment of the present disclosure;

FIG. 6 schematically shows a schematic diagram of a mask alignment mark and a substrate alignment mark according to an embodiment of the present disclosure;

Fig. 7 schematically shows a gap measurement optical path diagram and an alignment measurement optical path diagram according to an embodiment of the present disclosure;

Description of reference signs:

1 Six-degree-of-freedom nano sports platform; 2 Film platform;

3 Silicon wafer to be exposed; 4 Exposure mask;

5 Motherboard; 6 Mask clamping device;

7 Substrate alignment mark; 8 Mask gap measurement mark;

9 Mask alignment mark; 10 Illumination light source lens;

100\200 The first and second X\Y axis translation stages;

101\201 The first and second Rz-axis rotating tables;

102\202 The first and second tilt adapter plates;

103\203 The first and second Z-axis translation stages;

104\204 The first and second Rx/Ry rotary tables;

105\205 The first and second lens holders;

106\206 The first and second telecentric lenses;

107\207 The first and second CCD cameras;

108\208 The first and second crystal oscillators;

109\209 The first and second laser light sources.

Detailed ways

In order to make the objectives, technical solutions, and advantages of the present disclosure clearer, the following further describes the present disclosure in detail in conjunction with specific embodiments and with reference to the accompanying drawings.

The embodiments of the present disclosure provide an alignment and measurement system, method, and lithography machine, which take into account alignment and focus leveling, and use the same set of detection systems to achieve horizontal alignment deviation measurement in the lithography process , And realized the vertical gap value measurement. Through the dark-field diffraction imaging technology, both the nano-scale online alignment detection between the substrate and the mask and the nano-scale online gap detection are taken into account. In addition, for near-field lithography systems, such as SP lithography systems and nanoimprint systems, the use of this system and alignment detection methods can greatly reduce the space requirements of the whole machine.

Fig. 1 schematically shows a structural diagram of the entire structure of the alignment and measurement system according to an embodiment of the present disclosure, including at least three sets of off-axis detection imaging optical paths, and each set of off-axis detection imaging optical paths includes: a laser light source 109 for The laser beam is emitted; the telecentric lens 106 is used to incident the laser beam on the surface of the mask at the Littrow angle, and the diffraction image is imaged on the CCD camera 107; the CCD camera 107 is set above the telecentric lens 106, and the beam passes through The diffraction of the mask gap measurement mark is imaged on the CCD camera 107, and the vertical gap value between the mask and the substrate is obtained according to the diffraction image information; at the same time, the light beam is diffracted by the mask alignment mark and the substrate alignment mark, A moiré fringe is formed on the CCD camera 107, and the horizontal alignment deviation value of the mask and the substrate is obtained based on the information of the moiré fringe.

According to the present disclosure, a gap measurement mark and an alignment mark are provided on the mask, and an alignment mark is provided on the substrate. Further, the gap measurement grating is composed of two groups of chirped gratings with reversed phases. The chirped grating preferably has a fixed period in the X direction but not a fixed period in the Y direction. The alignment mark on the mask is a periodic grating alignment mark, and the alignment mark on the substrate is a periodic grating reflection alignment mark.

The off-axis detection imaging optical path is set on the substrate and the mask. The light beam emitted by the laser light source module is decohered by the crystal oscillator and collimated by the collimator lens, and then guided to the telecentric lens, and then irradiated to the telecentric lens with the designed gap measurement angle In the chirped grating pattern area of the mask, the telecentric lens images the diffraction pattern of the chirped grating onto the CCD camera. Through frequency + phase analysis of the diffraction image, the vertical nanometer-scale online gap measurement is realized; The alignment measurement angle is irradiated to the alignment pattern area of the mask. The alignment measurement angle is equal to the gap measurement angle. After the beam is diffracted by the periodic grating on the mask, it irradiates the alignment mark of the substrate and passes through the and mask of the substrate. The checkerboard grating with a certain difference in the mode grating period is diffracted and returned to the telecentric lens according to the original optical path. The telecentric lens images the aligned image onto the CCD camera, and realizes the horizontal nanometer by analyzing the phase information of the aligned moiré fringe. Magnitude of online alignment deviation detection.

That is to say, this system takes into account both focusing and leveling and precise alignment. The dark-field moiré fringe alignment deviation detection function and the chirped grating gap detection function are integrated into a set of detection units, and the vertical measurement system and the horizontal measurement system are realized. The integrated structure reduces the space requirement of the complete system of the lithography machine, and saves the space occupancy rate of the lithography machine; the measurement system that takes into account alignment and focusing and leveling realizes the focus and leveling of the substrate at the same time. Alignment improves the working efficiency of the lithography machine.

The telecentric lens 106 is a graphic imaging lens, which mainly images the diffraction fringes of the chirped grating on the mask or the dark-field moiré fringes between the mask and the substrate to the CCD camera. The resolution of the telecentric lens 106 is selected according to the design value, and functions such as noise removal can be realized. The CCD camera 107 is the core unit of imaging, and its pixel size is related to the measurement accuracy and mainly provides high-quality pictures for the algorithm. The laser light source 109 is used to provide illumination light of a stable wavelength.

Here, the alignment measurement angle and the gap measurement angle are set to be equal, both are incident at the Litro angle, and the incident light and the diffracted light are in a self-collimating state, that is, the incident light and the exit light follow the same path. The light beam is diffracted by the alignment mark grating and chirped grating on the mask, and finally irradiates the alignment mark of the substrate. After reflection, the diffracted beam returns to the telecentric lens in the original way, and is transferred by the imaging objective lens of the telecentric lens. The diffraction image is imaged to the image surface of the CCD camera connected to the telecentric lens. By calculating the diffraction image information obtained by the CCD camera, the vertical gap value and the horizontal alignment deviation value can be obtained. According to the result, the workpiece table is driven to complete the position adjustment of the substrate to be tested, and realize the alignment of the mask and the substrate. Quasi-operation.

It should be noted that there are at least three sets of off-axis detection imaging light paths to achieve leveling between the planes, and the angles between the planes are obtained through the data of the three-component imaging light paths. Three groups or more of off-axis detection imaging optical paths are symmetrically and evenly distributed around the mask to achieve more precise alignment and measurement. Compared with the traditional industrial lens, the telecentric lens 106 can correct the lens parallax, and within a certain object distance range, the obtained image magnification will not change, so as to reduce the imaging error.

The light beam emitted by the laser light source is diffracted by the chirped grating. The telecentric lens captures the interference image and images it on the CCD camera. The detection grating on the mask is composed of two groups of chirped gratings with opposite phases. The telecentric lens collects the left and right sides. Group interference patterns, when the gap between the mask and the substrate increases, a higher fringe frequency is produced; on the contrary, when the gap between the mask and the substrate decreases, the difference in the fringe period becomes smaller. Using the spatial phase information of the left and right sets of interference fringes and adopting an accurate phase analysis method, the gap value of the nanometer order can be obtained. At the same time, the beam is irradiated on the alignment mark of the mask, and the beam diffracted by the grating on the mask is irradiated on the alignment image of the substrate, and then diffracted again to form a magnified period of moiré fringe image. The two spatial frequencies are similar. The optical fringe formed by the superimposition of the periodic grating patterns of the optical fringe is the Moiré fringe. The image is captured by the telecentric lens and imaged on the CCD camera. Based on the similar spatial phase method, the two sets of coarse and fine fringes on the left and right sides of the direction to be measured are analyzed. Phase value to calculate the offset value of the horizontal alignment between the mask and the substrate to be tested.

On the basis of the foregoing embodiment, it further includes a six-degree-of-freedom lens attitude adjustment mechanism matching the off-axis detection imaging optical path, and the off-axis detection imaging optical path is fixed on the six-degree-of-freedom lens attitude adjustment mechanism.

The six-degree-of-freedom lens attitude adjustment mechanism is fixed with the off-axis detection imaging optical path, which is used to adjust the position of the off-axis detection imaging optical path relative to the mask, so that the light beam emitted by the off-axis detection imaging optical path is incident on the surface of the mask at a Litro angle. And receive the reflected beam.

On the basis of the above embodiment, the six-degree-of-freedom lens attitude adjustment mechanism includes: X/Y-axis translation stage 100; Rz-axis rotation stage 101, which is mounted on X/Y-axis translation stage 100; and tilt adapter plate 102, which It is installed on the Rz-axis rotating stage 101 and includes an inclined surface; the Z-axis translation stage 103 is installed on the inclined surface of the inclined adapter plate 102; and the Rx/Ry rotating stage 104 is installed on the Z-axis translation stage 103.

FIG. 3 schematically shows a structural diagram of the alignment and measurement system according to an embodiment of the present disclosure. Please refer to FIG. The axis rotation stage can adjust the position and angle relationship between the telecentric lens and the mask alignment pattern area and the gap measurement pattern area; by adjusting the X-axis translation stage and the Z-axis translation stage, the telecentric lens can be adjusted; by rotating The stage can adjust the incident angle of the incident laser to meet the angular relationship with the telecentric lens.

On the basis of the foregoing embodiment, the six-degree-of-freedom lens attitude adjustment mechanism is used to adjust the attitude of the off-axis detection imaging optical path in the six-degree-of-freedom direction, and adjust the incident position and angle of the light beam.

The six-degree-of-freedom lens attitude adjustment mechanism is used to assist the off-axis detection and imaging optical path to complete the movement of the upper platform in the six degrees of freedom (X, Y, Z, α, β, γ) in space, so as to simulate various spatial motion attitudes. Adjust the position and angle relationship between the telecentric lens and the mask alignment pattern area and the gap measurement pattern area.

On the basis of the above embodiment, the six-degree-of-freedom lens attitude adjustment mechanism further includes: a lens holder 105, which is installed on the Rx/Ry rotating stage 104 and used to keep the telecentric lens 106 and the CCD camera 107 stable. The telecentric lens 106 is connected to the CCD camera 107 and clamped on the lens holder 105. The light source collimation module is installed on the illumination light source inlet of the telecentric lens. The lens holder 105 is used to fix the telecentric lens 106 and the CCD camera 107. , Please refer to FIG. 3, which also includes a first lens holder 105, a first telecentric lens 106, a first CCD camera 107, a first crystal oscillator 108, and a first laser light source 109.

On the basis of the foregoing embodiment, the off-axis detection imaging optical path further includes: a crystal oscillator module 108 for eliminating the coherence of the laser.

Because the laser has extremely high coherence, there will be obvious interference fringes on the illumination surface. The crystal oscillator module 108 eliminates the laser coherence characteristics, avoids image related noise, and avoids the production of coherent rings on the image collected by the CCD to improve The quality of image formation.

On the basis of the foregoing embodiment, the light beam emitted from the off-axis detection imaging optical path obliquely irradiates the surface of the mask 4 without affecting the exposure of the substrate.

The light beam is incident on the mask mark obliquely. On the one hand, it avoids interference with the spatial position of the illumination light source and realizes the online alignment deviation detection function; on the other hand, it only collects the diffraction order light of interest, which enhances the image contrast.

Another embodiment of the present disclosure provides an alignment and measurement method, including: a CCD camera 107 collects a diffraction image of a mask gap measurement mark, and obtains the vertical gap value between the mask and the substrate according to the diffraction image information; The CCD camera 107 collects the moiré fringe formed by the diffraction of the mask alignment mark and the substrate alignment mark, and obtains the horizontal alignment deviation value of the mask and the substrate according to the information of the moiré fringe; according to the vertical gap value Adjust the position of the substrate with the horizontal alignment deviation value, and realize the alignment of the mask and the substrate.

The laser light source module emits a laser beam, the beam is eliminated by the crystal oscillator, and then the beam is collimated by the collimating lens, and then the beam is introduced into the telecentric lens through the light guide, and irradiated to the mask at a certain angle obliquely Alignment marks and chirped grating. Adjust the CCD lens to focus, collect the diffraction image of the chirped grating, and calculate the vertical gap value between the substrate to be tested and the lower surface of the mask; at the same time, collect the diffraction formed by the mask alignment mark and the substrate alignment mark. Calculate the horizontal alignment deviation value between the mask and the substrate to be tested; feedback the vertical gap value to the substrate control system, drive the workpiece table, and complete the position adjustment of the substrate to be tested; The quasi-deviation value is fed back to the substrate control system, and the workpiece table is driven to complete the position adjustment of the substrate to be tested, so as to realize the alignment operation of the mask and the substrate.

On the basis of the foregoing embodiment, before the CCD camera 107 collects the image, it also includes: a six-degree-of-freedom lens attitude adjustment mechanism adjusts the imaging optical path of the CCD camera 107, so that the chirped grating mark and the alignment mark on the mask are at the same time in the imaging optical path. Central region.

Before acquiring the image, it also includes: adjusting the imaging optical path of the telecentric lens through the six-degree-of-freedom motion stage, so that the mask gap measurement mark and the mask alignment mark are at the center of the imaging optical path at the same time, which is convenient for image acquisition.

Another embodiment of the present disclosure provides a lithography machine, which includes a mask and a workpiece table, and also includes the aforementioned alignment and measurement system.

The alignment and measurement system of the present disclosure can be used in a lithography machine to accurately establish the relationship between various coordinate systems of the lithography machine, so that a uniform positional relationship can be established for the mask, the objective lens, and the stage.

The alignment and measurement system and its measurement method not only realize the detection of nano-scale online alignment deviation between the mask and the substrate, but also realize the detection of the nano-scale online gap between the mask and the substrate; through the introduction of 3 A group or more than 3 groups of measurement systems can realize the focus leveling and precise alignment of the mask and the substrate; the measurement system and detection method do not affect the exposure of the pattern area, which reduces the space requirement of the lithography machine, and can also Real-time detection of the alignment deviation between the mask and the substrate and whether the substrate is out of focus and other states during the exposure are judged to ensure that the desired accuracy index is achieved.

In the present disclosure, the two results of the vertical gap value and the horizontal alignment deviation value are obtained through the collected images or data. There are two implementation methods: one implementation method is to place the gap measurement mark next to the alignment mark, and The incident angle of the light source for the gap measurement is designed to be aligned with the incident angle of the light source. At this time, the graph of the gap measurement and the aligned image can be directly imaged on the CCD at the same time, which is equivalent to analyzing the images of different positions of an image. Simultaneous measurement of gap and alignment deviation. Another way to achieve this is to separate the alignment image from the substrate to avoid mutual interference between the two images. At this time, when measuring the gap value, the CCD acquires the image of the gap measurement. When the alignment value is to be measured, move the CCD The lens position, to obtain the image of the alignment measurement.

Hereinafter, the present disclosure will be described in detail with a specific embodiment in conjunction with the accompanying drawings.

Figure 1 is a structural diagram of the whole machine of the alignment and measurement system. The measurement system includes a six-degree-of-freedom nano-motion stage 1; a carrier stage 2, which is mounted on the six-degree-of-freedom nano-motion stage 1; a silicon wafer to be exposed 3; and an exposure mask The mold 4 is fixed by the mask holding device 6; the main substrate 5; the mask holding device 6 is fixed to the main substrate 5; the substrate alignment mark 7; the mask gap measurement mark 8; the mask alignment mark area 9; Illumination light source lens 10; first and second X\Y-axis translation stages 100\200; first and second Rz-axis rotation stages 101\201, respectively installed on the first and second X\Y-axis translation stages 100 \200; the first and second tilt adapter plates 102\202 are installed on the first and second Rz-axis rotation stages 101\201 respectively; the first and second Z-axis translation stages 103\203, and the first , The second Rz-axis rotating stage 101\201 is connected to the first and second Rx/Ry rotating stages 104\204, respectively, and is used to adjust the focus of the CCD camera; the first and second Rx/Ry rotating stages 104\204; 1. The second lens holder 105\205 is used to fix the telecentric lens 106\206; the first and second telecentric lens 106\206; the first and second CCD camera 107\207 are used for image acquisition ; The first and second crystal oscillators 108\208 are used to eliminate laser coherence characteristics; the first and second laser light sources 109\209. Among them, the same detection system is used for the gap value and alignment deviation value between the mask and the substrate, which reduces the space occupancy rate of the lithography machine, and realizes online alignment deviation detection and gap value measurement.

Figure 2 is a top view of the overall structure of the lithography device of the alignment and measurement system in this embodiment; among them, 7-1, 7-2, 7-3, 7-4, 7-5, 7-6, 7-7 , 7-8 are the first to eighth group of substrate alignment marks; 10-1, 20-1, 30-1, 40-1, 50-1, 60-1, 70-1, 80-1 They are the first to eighth sets of alignment deviation measurement modules. 8 sets of the same alignment deviation detection modules are installed in two sets on the four corners of the graphic area. This layout is more conducive to detecting the overall image level. Alignment deviation, each set of alignment deviation detection module has the function of precise posture adjustment of the telecentric lens.

Fig. 4 is a schematic diagram of the optical path for measuring and detecting the gap between the mask and the substrate and the optical path for detecting the alignment deviation of the present disclosure. 8-1, 8-2, 8-3, and 8-4 are the first to fourth groups of gap measurement marks; 9-1, 9-2, 9-3, 9-4, 9-5, 9- 6, 9-7, and 9-8 are the first to eighth groups of mask alignment marks; 28 is the mask pattern area; the alignment marks are arranged on the four corners of the entire pattern area, and 4 sets of marks are used for Measure the alignment deviation in the X direction, and the other 4 groups are used to measure the alignment deviation in the Y direction. The gap measurement marks are arranged next to the 4 sets of Y-direction alignment marks, and an appropriate decoupling algorithm is designed to obtain the Z gap value between the mask and the substrate, and the yaw angle in the Rx and Ry directions. The left picture is the optical path diagram of the gap measurement. The beam emitted by the laser light source passes through the crystal oscillator to eliminate the coherence. Then, the beam is irradiated to the gap measurement mark at an angle α to the normal direction of the mask after passing through the lens group expansion collimation module Above, after the diffraction of the chirped grating, the telecentric lens captures the interference image and images it on the CCD camera. Its design feature is that the laser beam irradiation angle is consistent with the diffraction imaging angle. The picture on the right is the alignment measurement optical path diagram. The beam emitted by the laser light source passes through the crystal oscillator to eliminate the coherence. Then, the beam passes through the lens group beam expansion collimation module and then irradiates the alignment mark of the mask at an angle of θ, and passes through the mask. The light beam diffracted by the grating on the mold irradiates the alignment image of the substrate, and forms a moiré image with a magnified period after being diffracted again. The image is captured by the telecentric lens and imaged on the CCD camera. Designing the alignment angle and the angle of the gap measurement to be the same angle, just to make the measurement system take into account the alignment and focusing and leveling functions. Fig. 7 shows the corresponding optical path diagram for gap measurement and alignment measurement optical path diagram. In order to use a set of systems to balance focusing, leveling and alignment, the incident angle of the gap measurement beam here is equal to the incident angle of the alignment beam.

Fig. 5 is a schematic diagram of the mask gap measurement grating mark of the present disclosure; among them, 8-01 and 8-02 are the first and second groups of mask gap measurement marks, respectively, used for gap measurement; the detection grating consists of two sets of phases Reversed chirped grating composition. The period of the detection grating in the X direction is fixed, but the period in the Y direction is not fixed. When a single-wavelength laser beam irradiates the detection mark at the designed Litro angle, the telecentric lens can collect interference patterns, including the left and right sets of interference patterns. When the gap between the mask and the substrate increases, a higher fringe frequency is generated; on the contrary, when the gap between the mask and the substrate decreases, the difference in the fringe period becomes smaller. The detection is not sensitive to whether the mask is aligned with the substrate, and does not require any pattern on the substrate, and can also be used in the exposure of the mark pattern of the 0th layer of the substrate. Using the spatial phase information of the left and right sets of interference fringes and adopting an accurate phase analysis method, the gap value of the nanometer order can be obtained.

In this embodiment, the gradient grating equation is as follows:

p(x)=(Kx+B) ^-C

p(x) represents the grating period at the x position, and K and B can be used to adjust the frequency and phase information of the interference fringes. The C parameter can adjust the gradual rate of the period of the grating. The frequency and phase of interference fringes are closely related to the grating period equation. Gradient gratings can be designed through numerical simulation to make the frequency and spacing have a linear proportional relationship. At the same time, the phase also increases or decreases linearly with the increase or decrease of the distance. The phase is very sensitive to the change of the pitch, and a period of phase change corresponds to the change of the pitch of _{p t.} Therefore, the phase measurement interval using interference patterns has high sensitivity.

According to the measured phase information, the amount of change in the gap can be calculated. The calculation formula is as follows:

Here, p _x1 and p _x2 are the grating periods at positions _{x 1} and x ₂ during gap measurement, _{and φ t} is the phase difference of the two sets of interference fringes during gap measurement.

FIG. 6 is a schematic diagram of the alignment deviation grating mark of the present disclosure. The figure on the left shows the detection of alignment deviation marks in the X direction. In this embodiment, the substrate X-direction moiré alignment mark 7-03 and the mask X-direction moiré alignment mark 9 are realized in a dark field environment. -03 Moiré fringe produced by diffraction. The substrate X-direction moiré alignment mark 7-03 is designed as the two-dimensional grating shown in Fig. 6, which is a fine alignment mark on the substrate, and the mask X-direction moiré alignment mark 9-03 is designed It is the one-dimensional grating shown in Figure 6. The mask X-direction moiré alignment mark 9-03 is a diffraction grating having a period in the X direction, and the period is slightly different from the period in the second diffraction grating. The substrate X-direction moiré alignment mark 7-03 is a diffraction grating having periods in the X-direction and the Y-direction. At the same time, a diffraction grating having a moiré period in the Y direction (the substrate Y-direction moiré alignment mark 7-01 and the mask Y-direction moiré alignment mark 9-01) are respectively arranged on the mask and the substrate. , Used to extend the detection range of the moiré fringe in the X direction. The right side of Figure 6 is the detection of the Y-direction alignment deviation mark, which realizes the diffraction produced by the substrate Y-direction Moiré alignment mark 7-01 and the mask Y-direction Moiré alignment mark 9-01 in the dark field environment Moiré fringe, one is set as the diffraction grating shown on the right side of Fig. 6, and the substrate Y-direction moiré fringe alignment mark 7-01 is set as the diffraction grating with a two-dimensional structure as shown on the right side of Fig. 6 . The mask Y-direction moiré alignment mark 9-01 is a diffraction grating having a period in the Y direction, which is a period different from the period in the second diffraction grating. The substrate Y-direction moiré alignment mark 7-01 is a diffraction grating having periods in the Y-direction and the X-direction. In addition, the mask Y-direction coarse alignment mark 9-00 and the substrate Y-direction coarse alignment mark 7-00 are used for coarse alignment in the Y direction to expand the detection range of the moiré fringe. Note that the first direction and the second direction are not limited to being arranged perpendicular to each other. In this embodiment, the magnification of the moiré fringe:

Here P _m is the magnification of the moiré fringe, and P ₁ and P ₂ are the grating period of the alignment mark on the substrate and the mask respectively (as shown in Fig. 6, the substrate alignment mark in the X or Y direction P1 corresponds to P2 of the mask alignment mark, and P2 of the substrate alignment mark corresponds to P1 of the mask alignment mark)

When calculating the alignment deviation, first use the phase analysis method to calculate the phase difference of the two groups of moiré fringes, _{expressed as Φ moire} . The alignment deviation can be calculated by the following formula:

Here Δx is the alignment shift value, Φ _moire fringe phase difference of the two moire.

Schematic diagram of the alignment deviation grating mark.

Referring to Figure 1 to Figure 4, the operation flow of the detection system is as follows:

Step 1: Power-on reset, adjust the posture of the telecentric lens through the six-degree-of-freedom motion stage, so that the collimated measurement beam is incident on the center area of the gap measurement mark and alignment mark of the mask at a litero angle to ensure that the CCD can be used at the same time Collect the gap measurement interference image and align the interference image;

Step 2: Adjust the Z-axis position of the moving table to focus the CCD lens, collect the diffraction image of the chirped grating on the mask, and analyze the frequency distribution of fringes and the phase difference between the left and right groups of fringes based on the spatial phase analysis method, and then calculate The vertical gap value between the upper surface of the substrate to be tested and the lower surface of the mask is obtained; at the same time, the moiré pattern formed by diffraction of the mask alignment mark and the substrate alignment mark is collected, and based on the similar spatial phase method, the to be analyzed The phase values of the two sets of coarse and fine stripes on the left and right of the measurement direction are calculated to calculate the horizontal alignment deviation of the mask and the substrate to be tested.

Step 3: Using 4 sets of gap measurement values on the mask, using geometric change method, you can get the position relationship between the substrate and the mask, including the vertical gap value, Rx and Ry yaw angle and other information, where the yaw The angle is the inclination angle between the mask and the substrate around the X axis. When the angle is larger, it means that the mask and the substrate have not been leveled. A substrate focusing and leveling control system with the vertical gap value, Rx and Ry yaw angles as feedback signals and nano-motion as the actuator is established to realize the focus and leveling operation of the mask and the substrate.

Step 4: Use 8 sets of alignment marks on the mask and the substrate to calculate the alignment deviation value between the mask and the substrate; establish a substrate alignment control system with the alignment deviation as a feedback signal, and adjust the substrate through the nano-motion stage The posture of the film in the horizontal direction realizes the alignment operation of the mask and the substrate.

The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present disclosure in further detail. It should be understood that the above are only specific embodiments of the present disclosure and are not intended to limit the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims (18)

1. An alignment and measurement system, characterized in that it comprises at least three sets of off-axis detection and imaging optical paths, and each set of off-axis detection and imaging optical paths includes:

   The laser light source (109) is used to emit a laser beam;

   The telecentric lens (106) is used to incident the laser beam on the surface of the mask (4) at a Litro angle, and to image the diffraction image on the CCD camera (107);

   The CCD camera (107) is arranged above the telecentric lens (106). The beam passes through the mask gap to measure the diffraction of the mark and then forms an image on the CCD camera (107). According to the diffraction image information, the mask and the The vertical gap value of the substrate; at the same time, the light beam is diffracted by the mask alignment mark and the substrate alignment mark to form moiré fringes on the CCD camera (107), and the moiré fringe information is obtained The offset value of the horizontal alignment of the mask and the substrate.
2. The alignment and measurement system according to claim 1, further comprising a six-degree-of-freedom lens attitude adjustment mechanism matching the off-axis detection imaging optical path, and the off-axis detection imaging optical path is fixed to the six Degree of freedom lens posture adjustment mechanism.
3. The alignment and measurement system according to claim 2, wherein the six-degree-of-freedom lens attitude adjustment mechanism comprises:

   X/Y axis translation stage (100);

   Rz-axis rotation stage (101), which is installed on the X/Y-axis translation stage (100);

   Inclined adapter plate (102), which is installed on the Rz-axis rotating table (101) and includes an inclined surface;

   Z-axis displacement stage (103), which is installed on the inclined surface of the inclined adapter plate (102);

   The Rx/Ry rotating stage (104) is installed on the Z-axis translation stage (103).
4. The alignment and measurement system according to claim 3, wherein the six-degree-of-freedom lens attitude adjustment mechanism is used to adjust the attitude of the off-axis detection imaging optical path in the six-degree-of-freedom direction, and adjust the The incident position and angle of the beam.
5. The alignment and measurement system according to claim 4, wherein the six-degree-of-freedom lens attitude adjustment mechanism further comprises:

   A lens holder (105) is installed on the Rx/Ry rotating table (104) and used to keep the telecentric lens (106) and the CCD camera (107) stable.
6. The alignment and measurement system according to claim 1, wherein the off-axis detection imaging optical path further comprises:

   The crystal oscillator module (108) is used to eliminate the coherence of the laser.
7. The alignment and measurement system according to claim 1, wherein the light beam emitted from the off-axis detection imaging optical path obliquely irradiates the surface of the mask (4) without affecting the exposure of the substrate.
8. The alignment and measurement system according to claim 1, wherein the mask gap measurement mark is composed of two sets of chirped gratings with opposite phases, and the mask alignment mark is a periodic grating alignment mark, The substrate alignment mark is a periodic grating reflection alignment mark.
9. A method of alignment and measurement, characterized in that it comprises:

   A CCD camera (107) collects the diffraction image of the mask gap measurement mark, and obtains the vertical gap value between the mask and the substrate according to the diffraction image information;

   At the same time, the CCD camera (107) collects the moiré fringe formed by diffraction of the mask alignment mark and the substrate alignment mark, and obtains the horizontal alignment deviation value of the mask and the substrate according to the information of the moiré fringe;

   The position of the substrate is adjusted according to the vertical gap value and the horizontal alignment deviation value, and the mask and the substrate are aligned.
10. The method of alignment and measurement according to claim 9, characterized in that, before the CCD camera (107) collects an image, the method further comprises:

    The six-degree-of-freedom lens posture adjustment mechanism adjusts the imaging light path of the CCD camera (107), so that the mask gap measurement mark and the mask alignment mark are located in the center area of the imaging light path at the same time.
11. A photoetching machine, comprising a mask and a workpiece table, is characterized in that it also comprises the alignment and measurement system according to any one of claims 1-8.
12. A measurement system that takes into account both focusing and leveling and precise alignment is arranged on a substrate and a mask, and is characterized in that: the measurement system that takes into account both alignment and focus and leveling includes three groups or more than three groups of six Freedom lens posture adjustment mechanism and off-axis detection imaging optical path, said off-axis imaging optical path is incident on the surface of the mask at a litero angle with the normal direction of the mask, and the measurement system that takes into account both alignment and focusing and leveling One set of six-degree-of-freedom lens attitude adjustment mechanism and off-axis detection imaging optical path includes X/Y-axis translation stage (100), Tz-axis rotation stage (101), tilt adapter plate (102), and Z-axis translation stage (103) , Rx/Ry rotating stage (104), lens holder (105), telecentric lens (106), CCD (107), crystal oscillator module (108) and alignment laser light source (109), in which the Tz axis rotates The stage (101) is installed on the X/Y-axis translation stage (100), the tilt adapter plate (102) is installed on the Tz-axis rotating stage (101), and the Z-axis translation stage (103) is installed on the tilt adapter plate (102). ), the Rx/Ry rotating stage (104) is installed on the Z-axis translation stage (103), the lens mounting plate (105) is installed on the Rx/Ry rotating stage (104), the telecentric lens (106) and CCD (107) The connection is clamped on the lens holder (105), and the light source collimation module is installed on the illumination light source inlet of the telecentric lens.
13. The measurement system of claim 12, wherein the off-axis imaging optical path includes a laser light source module, a laser decoherence module, and a light source alignment in sequence along the beam propagation direction. Straight lens, telecentric lens with light guide device and CCD camera, the light beam emitted by the laser light source module is decohered by the crystal oscillator and collimated by the collimator lens and then guided to the telecentric lens, and then irradiated with the designed gap measurement angle To the chirped grating pattern area of the mask, the telecentric lens images the diffraction pattern of the chirped grating onto the CCD, and performs frequency+phase analysis on the diffraction image to achieve vertical nanometer-scale online gap measurement.
14. The measurement system of claim 13, wherein the off-axis imaging optical path includes a laser light source module, a laser decoherence module, and a light source alignment in sequence along the beam propagation direction. A straight lens, a telecentric lens with a light source lead-in interface and a CCD camera. The light beam emitted by the laser light source module is decohered by the crystal oscillator and collimated by the collimator lens, then poured into the telecentric lens, and then aligned as designed The measurement angle is irradiated to the alignment pattern area of the mask, and the alignment measurement angle is equal to the gap measurement angle. The beam is diffracted by the periodic grating on the mask and irradiated to the alignment mark area of the substrate, and passes through the grating of the substrate and the mask. The checkerboard grating with a certain period difference is diffracted and then returned to the telecentric lens according to the original optical path. The telecentric lens images the aligned image onto the CCD camera. By analyzing the phase information of the aligned moiré fringe, the horizontal nanometer order is realized. Online alignment deviation detection.
15. The measurement system of claim 13, wherein a chirped grating calibration mark and a periodic grating alignment mark are provided on the mask.
16. The measurement system for focusing and leveling and precise alignment according to claim 13, wherein the substrate is provided with a periodic grating reflection alignment mark.
17. A measurement method that takes into account both focusing and leveling and precise alignment adopts the measurement system that takes into account both alignment and focus and leveling according to claim 13, characterized in that it comprises the following steps:

    Step 1: Adjust the imaging optical path of the telecentric lens through the six-degree-of-freedom motion stage, so that the chirped grating mark and the alignment mark on the mask are at the center of the imaging optical path at the same time;

    Step 2: Adjust the CCD lens to focus, collect the diffraction image of the chirped grating, and calculate the vertical gap value between the substrate to be tested and the lower surface of the mask; at the same time, collect the diffraction from the mask alignment mark and the substrate alignment mark Calculate the horizontal alignment deviation of the mask and the substrate to be tested for the formed moiré pattern;

    Step 3: Feedback the vertical gap value to the substrate control system, drive the workpiece table, and complete the position adjustment of the substrate to be tested;

    Step 4: Feedback the horizontal alignment deviation value to the substrate control system, drive the workpiece table, complete the position adjustment of the substrate to be tested, and realize the alignment operation of the mask and the substrate.
18. A photoetching machine, comprising a mask and a workpiece table, characterized in that: the photoetching machine further comprises the measurement system of any one of claims 12-16 that takes into account both alignment and focusing and leveling.

Images