WO2016201788A1

WO2016201788A1 - In-situ multichannel imaging quality detection device and method for mask aligner

Info

Publication number: WO2016201788A1
Application number: PCT/CN2015/088311
Authority: WO
Inventors: 唐锋; 李�杰; 王向朝; 冯鹏; 徐世福; 卢云君
Original assignee: 中国科学院上海光学精密机械研究所
Priority date: 2015-06-15
Filing date: 2015-08-27
Publication date: 2016-12-22
Also published as: CN106324996B; CN106324996A

Abstract

An in-situ multichannel imaging quality detection device and method for a mask aligner. The device comprises a light source (1) of the mask aligner, a lighting system (2), a mask table (4), a projecting lens (5), a workbench (7),and a computer (8), and also comprises a object plane grating plate (3) and a wave aberration sensor (6). By using the device, imaging quality, related to wave aberration, distortion and field curvature, of the mask aligner is detected in situ, thereby increasing the number of parallel channels and the detection speed of the imaging quality detection.

Description

In-situ multi-channel imaging quality detecting device and method for lithography machine

Technical field

The invention relates to a lithography machine, in particular to a lithography machine in-situ multi-channel imaging quality detecting device and method.

Background technique

The lithography machine is one of the core devices for the manufacture of very large scale integrated circuits. The projection objective is one of the most important subsystems of the lithography machine. The imaging quality of the projection objective is one of the key factors determining the quality of the lithographic line. As the lithographic node progresses below 1x nm resolution, a yield of 250 wph is required. The increase of the yield causes the thermal effect of the lithography mask and the thermal aberration of the projection objective, which affects the precision of the lithography machine and the imaging quality of the projection objective. It is required to be able to measure the distortion, curvature of field and wave aberration of the lithography system in real time.

Generally, the lithography machine uses different sensors to detect distortion, field curvature and wave aberration parameters. The distortion and field curvature parameters are realized by the scanning of the aligning system of the lithography machine; the wave aberration is realized by the in-situ wave aberration sensor, and the full field wave aberration detection is realized by scanning. ASML in the Netherlands reported a multi-channel image quality sensor (refer to prior art [1], Wim de Boeij, Remi Pieternella, et al., Extending immersion lithography down to 1x nm production nodes. Proc. of SPIE Vol. 8683, 86831L (2013)), instead of the original TIS coaxial alignment and primary aberration detection functions such as distortion and field curvature, and parallel detection of 7 field-of-view point wave aberrations of the lithographic projection objective, wavefront detection result From the Z5 ~ Z37 Zernike coefficient to the Z2 ~ Z64 Zernike coefficient.

However, due to the limited pixel of the detector, simultaneously detecting the wave aberration of the seven field of view points will inevitably lead to the reduction of the number of effective detection pixels per field of view. Under the premise of ensuring the spatial resolution of the wave aberration detection (detecting the Z64Zernike coefficient) ), it is difficult to increase the number of parallel channels detected. Increasing the number of parallel channels for detection can improve the accuracy of distortion and field curvature detection, and improve the accuracy of thermal effect prediction.

On the other hand, the in-situ imaging quality detection speed is an important factor affecting the productivity of the lithography machine. Increasing the in-situ imaging quality detection speed is also an important aspect of the improvement of the in-situ imaging quality detection sensor.

Summary of the invention

It is an object of the present invention to provide an in-situ multi-channel imaging quality detecting apparatus and method for a lithography machine for quickly detecting in situ the wave aberration, distortion, and field curvature of a projection objective of a lithography machine.

The technical solution of the present invention is as follows:

A lithography machine in-situ multi-channel imaging quality detecting device, comprising: a light source of a lithography machine, an illumination system, a mask table, a projection objective lens, a workpiece table and a computer, characterized in that it further comprises a surface grating plate and a wave An aberration sensor; the object grating plate is placed on the mask table, the wave aberration sensor is placed on the workpiece table, and the wave aberration sensor is connected to the computer;

The object grating plate is composed of n sets of object gratings with a duty ratio of 50%; each set of surface gratings includes a first grating of the grating line along the y direction and a second grating of the grating line along the x direction, and the period is P _oX ;

The wave aberration sensor includes an image grating plate, a small hole array and a two-dimensional photoelectric sensor which are sequentially placed along a beam propagation direction;

The image surface grating plate comprises n sets of image plane gratings with a duty ratio of 50%, and the period is P _iX ;

The period P _oX of the first grating and the second grating and the period P _iX of the image plane grating satisfy the following relationship;

P _oX =P _iX ·M

Where M is the imaging magnification of the projection objective (5) of the lithography machine, and P _{iX is} determined by the shear rate s _X , the wavelength λ of the source, and the numerical aperture NA of the projection objective of the lithography machine:

The spacing d _o between each set of surface gratings on the object grating plate and the spacing d _i between each image surface grating on the image grating plate satisfy the following relationship:

d _o =d _i ·M,

The spacing between the first grating and the second grating of each set of surface gratings on the object grating plate is equal, and the number of group gratings is equal to the number of image plane gratings, all of which are n, and the n is greater than 1. Natural number.

The first grating and the second grating are a one-dimensional reflective grating or a one-dimensional transmissive grating of a phase grating or an amplitude grating type.

The period of the aperture array is equal to the pixel period of the photoelectric two-dimensional sensor, and the aperture position of the aperture array is in one-to-one correspondence with the pixel position of the photoelectric two-dimensional sensor, and the photoelectric two-dimensional sensor pixel The ratio of the size to the diameter of the aperture of the array of apertures is S.

The two-dimensional photosensor is a camera, CCD, CMOS image sensor, PEEM, or a two-dimensional photodetector array.

The image plane grating is a two-dimensional transmission grating of a phase grating or an amplitude grating type.

The detection method of the in-situ multi-channel imaging quality detecting device of the above lithography machine comprises the following steps:

1 placing the object grating plate on the mask table, adjusting the mask table, so that the n sets of the first grating of the object grating plate are located at the object field of view of the projection objective of the lithography machine;

2 after the light emitted by the light source is adjusted by the illumination system, uniformly illuminating the n sets of first gratings of the object grating plate;

3 placing the wave aberration sensor on the workpiece table, adjusting the workpiece table, so that the image grating plate is located on the image surface of the projection objective of the lithography machine;

4 adjusting the workpiece table such that the n sets of image surface gratings are respectively aligned with the image formed by the first grating of the n sets of surface gratings through the projection objective of the lithography machine;

5 using phase shifting technology, moving the workpiece table multiple times in the x direction, after each movement, the wave aberration sensor collects a shearing interferogram input to the computer, and the computer is obtained from the acquisition. The x-direction shear phase information of the n field of view points is calculated in the interferogram;

6 adjusting the mask table, so that the n sets of the second gratings of the object grating plate are respectively moved to the positions of the n sets of the first gratings, and the n sets of the second gratings are respectively formed by the image formed by the projection objective of the lithography machine and the n sets of the image gratings respectively alignment;

7 Using phase shifting technology, moving the workpiece table multiple times in the y direction. After each movement, the wave aberration sensor collects a shearing interferogram and inputs it into the computer, and the computer calculates from the acquired interferogram. Obtaining y-direction shear phase information of n field of view points;

8 unwrapping the shear phase information obtained in

steps

5 and 7, respectively, obtaining the shear wavefronts ΔW _x and ΔW _{y of the} projection objective of the lithography machine in the x and y directions at the n field of view points, respectively. The shear wavefront is reconstructed to obtain the wavefront aberration of the projection objective of the lithography machine at the n field of view points; the wavefront tilt and defocus data of the wavefront aberration from the n field of view points are calculated by the projection objective of the lithography machine Distortion and field curvature.

Compared with the prior art, the present invention has the following advantages:

1) The present invention introduces a small aperture array in a wavefront aberration sensor, and uses a small aperture array to increase the spatial resolution of the in-situ detection of imaging quality by S ² times, thereby effectively reducing the pixels used by the two-dimensional photoelectric sensor of each channel. Number, the number of parallel detection channels is improved, and the parallel detection channel can increase S ² times.

2) Since the number of pixels used by the two-dimensional photoelectric sensor per channel is reduced, the amount of data calculation is reduced, thereby improving the detection speed, and the detection speed can be increased by S ² times.

3) Through multi-channel simultaneous detection, the wavefront aberration sensor has the ability to simultaneously detect image quality parameters such as distortion and field curvature.

DRAWINGS

1 is a structural view of an in-situ multi-channel imaging quality detecting device of the lithography machine of the present invention.

Figure 2 is a schematic view of the object grating plate of the present invention.

Figure 3 is a schematic view showing the structure of a wave aberration sensor of the present invention.

Figure 4 is a schematic view of an image surface grating plate according to the present invention.

Figure 5 corresponds to the detection error of the apertureless array.

Figure 6 is equivalent to the detection error of the aperture array.

detailed description

The invention is further illustrated by the following examples and the accompanying drawings, but should not be construed as limiting the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram of an in-situ multi-channel imaging quality detecting apparatus of a lithography machine of the present invention. The in-situ multi-channel imaging quality detecting device of the lithography machine of the present invention comprises a light source 1, a lighting system 2, a mask table 4, a lithography projector objective lens 5, a workpiece table 7, and a masking table 4 a surface grating plate 3 and a wave aberration sensor 6 disposed on the workpiece stage 7 and a data processing computer 8 connected to the wave aberration sensor 6; the light source 1 of the present embodiment has a wavelength of 193 nm; n=14, The object grating plate 3 is composed of 14 sets of object gratings having a period of 41.52 μm and a duty ratio of 50% (see FIG. 2), including the first gratings 3A1 to 3N1 of the grating lines along the y direction and the grating lines along the x direction. The second gratings 3A2 to 3N2; the image plane grating plate 601 includes 14 groups of image plane gratings 601A to 601N having a duty ratio of 50%; the image plane gratings 601A to 601N adopt a two-dimensional checkerboard grating; and the image plane gratings 601A to 601N The period is 10.38 μm; the object grating and the image grating are transmissive amplitude gratings; the numerical aperture of the projection objective 5 of the lithography machine is 0.93, and the imaging magnification of the projection objective 5 of the lithography machine is 1/4, the shear rate 1%; the wave aberration sensor 6 (see Fig. 3) includes image grating plates placed in order along the direction of beam propagation 601, the aperture array 602 and the two-dimensional photoelectric sensor 603; the two-dimensional photoelectric sensor 603 uses a CMOS camera, the pixel size is 5.6 μm × 5.6 μm, the number of pixels is 2040 × 1084; the aperture size of the aperture array 602 is 1.4 μm, The ratio of the pixel size to the aperture diameter of the CMOS camera is 4, the period of the aperture array 602 is equal to 5.6 μm of the pixel period of the photodiode sensor 603, and the spacing between adjacent two-dimensional gratings 601X on the image plane grating 601 is 1.5 mm; The spacing between adjacent first gratings on the surface grating plate 3 and the spacing between adjacent second gratings are equal to 6 mm; the first grating 3X1 and the second grating 3X2 of each group of surface gratings on the object grating plate 3 The spacing between them is equal to 3mm.

The object grating plate 3 is composed of 14 sets of object gratings whose periods are both P _o and a duty ratio of 50%; each set of surface gratings includes a grating grating along the y direction of the first grating 3X1 and a grating line along the x The second grating 3X2 of the direction; the X is the number of each set of gratings, denoted by A, B, C, ..., N, such as the first grating 3A1 and the second grating 3A2 of the group A object grating, the group B object a first grating 3B1 and a second grating 3B2 of the grating;

The first grating 3X1 and the second grating 3X2 are diffraction gratings of a phase grating or an amplitude grating type;

The first grating 3X1 and the second grating 3X2 are reflective gratings or transmissive gratings;

The wave aberration sensor 6 includes an image surface grating plate 601, an aperture array 602 and a two-dimensional photoelectric sensor 603 which are sequentially placed in the beam propagation direction;

The image surface grating plate 601 (see FIG. 4) includes 14 sets of image surface gratings 601X having the same period and a duty ratio of 50%, and the X is the number of each set of gratings, and is represented by A, B, C, and the like;

The image plane grating 601X is a two-dimensional transmission grating of a checkerboard grating type;

The image plane grating 601X is a phase grating or an amplitude grating type diffraction grating;

The period P _o of the first object surface grating 3X1 and the second object surface grating 3X2 on the object grating plate 3 and the period P _i of the image plane grating 601X satisfy the following relationship:

P _o =P _i ·M,

Wherein, M is an imaging magnification of the projection objective 5 of the lithography machine; P _{i is} determined by a shear rate s, a wavelength λ of the light source, and a numerical aperture NA of the projection objective of the lithography machine;

The distance d _o between each set of surface gratings on the object grating plate 3 and the distance d _i between each set of image surface gratings on the image grating plate 601 satisfy the following relationship:

d _o =d _i ·M,

The spacing between the first grating 3X1 and the second grating 3X2 of the object grating on the object grating plate 3 is equal.

The period of the small holes on the aperture array 602 is equal to the period of the pixels on the photoelectric two-dimensional sensor 603, and the small hole position corresponds to the pixel position of the photoelectric two-dimensional sensor, and the small hole diameter is the pixel size of the photoelectric two-dimensional sensor 603. 1/4;

The mask table 4 is a displacement stage for moving the object grating plate 3 into the object optical path of the projection objective 5 of the lithography machine;

The workpiece stage 7 is a displacement stage for moving the wavefront aberration sensor 6 into the image side optical path of the projector objective lens 5 and driving the wave aberration sensor 6 to move;

The two-dimensional photosensor 603 is a camera, a CCD, a CMOS image sensor, a PEEM, or a two-dimensional photodetector array, the detection surface receives a shear interference image generated by the image plane grating 601X and sampled by the aperture array 602;

The computer 8 is used to control the wave aberration detection process, store measurement data, and process and analyze the interference map.

The detection method of the in-situ multi-channel imaging quality detecting device of the above lithography machine is adopted, and the steps of the method are as follows:

(1) placing the surface grating plate on the mask table, adjusting the mask table, so that the 14 sets of the first grating 3X1 are located at the object field of view position of the projection objective of the lithography machine;

(2) after the light emitted by the light source is adjusted by the illumination system, uniformly illuminating the 14 sets of first gratings 3X1 of the object grating plate;

(3) placing the wave aberration sensor 6 on the workpiece stage 7, and adjusting the workpiece stage 7, so that the image plane grating plate 601 is located on the image surface of the projection objective 5 of the lithography machine;

(4) adjusting the workpiece stage such that the 14 sets of image surface gratings 601X are respectively aligned with the images formed by the first grating 3X1 of the 14 sets of surface gratings through the projection objective of the lithography machine;

(5) Using the phase shift technique, the workpiece stage 7 is moved a plurality of times in the x direction. After each movement, the wave aberration sensor 603 collects a shearing interferogram, and the 14 field points calculated from the acquired interferogram are obtained. Shear phase information of the position in the x direction;

(6) adjusting the mask table 4 so that the 14 sets of the second gratings 3X2 of the object grating plate are respectively moved to the positions of the 14 sets of the first gratings 3X1, and the 14 sets of the second gratings 3X2 are imaged by the projection objective of the lithography machine. 14 sets of image plane gratings 601X are respectively aligned;

(7) Using the phase shift technique, the workpiece table 7 is moved a plurality of times in the y direction for measurement. After each movement, the wave aberration sensor 603 acquires a shear interferogram, and the 14 views calculated from the acquired interferogram are obtained. Shear phase information of the field position in the y direction;

(8) Unwrapping the shear phase information obtained in steps (5) and (7) to obtain the shear wavefronts ΔW _x and ΔW in the x and y directions of the projection objective of the lithography machine at 14 field points. _y , the shear wavefront is reconstructed to obtain the wavefront aberration of the projection objective of the lithography machine at 14 fields of view; the wavefront tilt and defocus data calculation of the wavefront aberration from 14 field of view points Distortion and field curvature of the projection objective.

The invention uses the aperture array to sample the wave aberration and increases the detection spatial resolution by S ² times. The simulation was performed using a 256 pixel × 256 pixel wave aberration (root mean square value of 0.0995 λ). The average value of every 4 pixels in the differential wavefront is equivalent to the absence of an aperture array, and a differential wavefront of 64 pixels × 64 pixels is obtained, and the differential wavefront is reconstructed. The error is shown in Fig. 5, and the error rms The value is 00141λ; the differential wavefront of the wave aberration is sampled, and one pixel is selected every 4 pixels, which is equivalent to adding a small hole array on the detector to obtain a differential wavefront of 64 pixels×64 pixels, and the differential wavefront is obtained. For reconstruction, the error is shown in Figure 6, and the rms error is 0.0001λ.

The embodiment proves that the device and the method of the invention improve the resolution of the projection object wavefront aberration detection by 16 times. Therefore, the number of channels of the in-situ multi-channel imaging quality detecting device of the lithography machine can be increased by 16 times and the detection speed is maximum. It can also be increased by 16 times. Through multi-channel simultaneous detection, the wavefront aberration sensor has the ability to simultaneously detect image quality parameters such as distortion and curvature of field.

Claims

A lithography machine in-situ multi-channel imaging quality detecting device, comprising: a light source (1) of a lithography machine, an illumination system (2), a mask table (4), a projection objective lens (5), and a workpiece table (7) And a computer (8), characterized in that it further comprises a surface grating plate (3) and a wave aberration sensor (6), and the connection relationship of the above components is as follows:

The object grating plate (3) is placed on a mask table (4), and the wave aberration sensor (6) is placed on a workpiece table (7), and the wave aberration sensor (6) is Computer (8) connected;

The object grating plate (3) is composed of n sets of object gratings having a duty ratio of 50%; each set of surface gratings includes a first grating (3X1) of the grating line along the y direction and a grating line along the x direction. The second grating (3X2) has a period of P oX ; the X is the number of each set of gratings, denoted by A, B, C, ..., such as the first grating 3A1 and the second grating 3A2, B of the group A object grating a first grating 3B1 and a second grating 3B2 of the group plane grating;

The wave aberration sensor (6) includes an image grating plate (601), an aperture array (602) and a two-dimensional photoelectric sensor (603) which are sequentially placed in the beam propagation direction;

The image surface grating plate (601) includes n sets of image plane gratings (601X) having a duty ratio of 50%, a period of P iX , and the X is a number of each set of gratings, denoted by A, B, C, ...;

Said first grating (3X1) and the second grating (3X2) with a period P oX image plane of the grating (601X) of the cycle satisfies the relation P iX;

P oX =P iX ·M

Where M is the imaging magnification of the projection objective (5) of the lithography machine, and P iX is determined by the shear rate s X , the wavelength λ of the source, and the numerical aperture NA of the projection objective of the lithography machine:

The distance d o between each set of surface gratings on the object grating plate (3) and the distance d i between each image surface grating on the image grating plate (601) satisfy the following relationship:

d o =d i ·M,

The spacing between the first grating (3X1) and the second grating (3X2) of each set of surface gratings on the object grating plate (3) is equal, and the number of group gratings is equal to the number of image plane gratings, both are n , the stated n is a natural number greater than one.
The in-situ multi-channel imaging quality detecting apparatus of the lithography apparatus according to claim 1, wherein the first grating (3X1) and the second grating (3X2) are one-dimensional reflections of a phase grating or an amplitude grating type. Grating or one-dimensional transmissive grating.
The in-situ multi-channel imaging quality detecting apparatus of the lithography apparatus according to claim 1, wherein the period of the aperture array (602) is equal to the pixel period of the photoelectric two-dimensional sensor (603), which is small. The aperture position of the aperture array (602) is in one-to-one correspondence with the pixel position of the photoelectric two-dimensional sensor (603), and the photoelectric two-dimensional sensor (603) has a pixel size and the aperture array (602) The ratio of the diameter of the small holes is S.
The in-situ multi-channel imaging quality detecting apparatus of the lithography apparatus according to claim 1, wherein the two-dimensional photosensor (603) is a camera, a CCD, a CMOS image sensor, a PEEM, or a two-dimensional photodetector. Array.
The in-situ multi-channel imaging quality detecting apparatus of the lithography apparatus according to claim 1, wherein the image plane grating (601X) is a two-dimensional transmissive grating of a phase grating or an amplitude grating type.
A method for detecting an in-situ multi-channel imaging quality detecting apparatus of a lithography apparatus according to any one of claims 1 to 5, characterized in that it comprises the following steps,

1 placing the object grating plate (3) on the mask table (4), adjusting the mask table (4), and making the first grating (3X1) of the object grating plate (3) Located at the object field of view of the projection objective (5) of the lithography machine;

2 after the light emitted by the light source (1) is adjusted by the illumination system (2), uniformly illuminating the n sets of first gratings (3X1) of the object grating plate (3);

3 Place the wave aberration sensor (6) on the workpiece table (7), adjust the workpiece table (7), and place the image grating plate (601) on the image surface of the projection objective (5) of the lithography machine;

4 adjusting the workpiece table (7) such that the n sets of image plane gratings (601X) are respectively aligned with the image formed by the first grating (3X1) of the n sets of surface gratings through the projection objective lens (5) of the lithography machine;

5 using a phase shifting technique, moving the workpiece table (7) multiple times in the x direction, and after each movement, the wave aberration sensor (6) acquires a shearing interferogram input to the computer, The computer calculates the x-direction shear phase information of the n field of view points from the acquired interferogram;

6 adjusting the mask table (4) so that the n sets of the second gratings (3X2) of the object grating plate (3) are respectively moved to the positions of the n sets of the first gratings (3X1), and the n sets of the second gratings (3X2) are passed through the light The image formed by the engraved projection objective lens (5) is aligned with the n sets of image plane gratings (601X);

7 using phase shifting technology, moving the workpiece table (7) multiple times in the y direction, after each movement, the wave aberration sensor (6) collects a shearing interferogram and inputs the computer into the computer, the computer collects The y-direction shear phase information of the n field of view points is calculated in the obtained interferogram;

8 unwrapping the shear phase information obtained in steps 5 and 7, respectively, obtaining the shear wavefronts ΔW x and ΔW y of the projection objective (5) in the x and y directions of the n field of view points, respectively. The shear wavefront is reconstructed to obtain the wavefront aberration of the projection objective lens (5) at the n field of view points; the wavefront tilt and defocus data calculation of the wavefront aberration from the n field of view points Distortion and field curvature of the projection objective (5) of the lithography machine.