CN109856923B

CN109856923B - Image quality compensation device and method and optical system

Info

Publication number: CN109856923B
Application number: CN201711267165.5A
Authority: CN
Inventors: 宋珊珊; 郭银章
Original assignee: Shanghai Micro Electronics Equipment Co Ltd
Current assignee: Shanghai Micro Electronics Equipment Co Ltd
Priority date: 2017-11-30
Filing date: 2017-11-30
Publication date: 2021-03-09
Anticipated expiration: 2037-11-30
Also published as: WO2019105443A1; TWI733066B; CN109856923A; TW201939168A

Abstract

The invention provides an image quality compensation device, which comprises a lens barrel, a force application mechanism and a rotating mechanism, wherein the force application mechanism applies pressure to the lens barrel to deform a lens in the lens barrel, and the lens barrel is positioned on the rotating mechanism and rotates along with the rotation of the rotating mechanism.

Description

Image quality compensation device and method and optical system

Technical Field

The present invention relates to the field of semiconductor integrated circuit manufacturing technology, and in particular, to an image quality compensation apparatus and method and an optical system.

Background

In the current field of semiconductor packaging technology, lithography objectives used to fabricate integrated circuit chips generally have high resolution, large depth of focus to enable the fabrication of highly integrated chips. Meanwhile, in order to meet the requirement that the image quality of an exposure area during chip preparation meets the requirement, an optical imaging system for projection exposure needs to have good image quality compensation capability. In order to meet the higher requirements of the product technology, the feature size of the chip needs to be continuously reduced, which puts more stringent requirements on the imaging quality of the optical system. Therefore, the improvement of the imaging quality of the optical imaging system becomes a key factor for preparing a chip with good comprehensive performance.

In the actual exposure process of the photoetching projection objective, due to assembly errors of lenses, environment instability and heat introduced by an illumination system, the lens surface shape can be influenced by the surrounding environment in the exposure process, and a certain amount of irreversible change can occur, all of which can cause the final imaging quality to be reduced, and the quality of the characteristic size of a chip is influenced.

In the prior art, in the exposure process of a photoetching projection objective, an image quality compensation scheme is realized by changing the lens surface type, but the scheme can only compensate single image quality. Or different surface types are generated by rotating the angle of the thermal compensation group and the angle of the flat plate combination to compensate the thermal effect, but the processing and detection difficulty of the special lens surface type of the thermal compensation group is high, and the cost is high.

Disclosure of Invention

The invention aims to provide a quality compensation device to solve the problems of single compensation, higher difficulty and higher cost of the existing image quality compensation scheme.

Optionally, the force application mechanism is located on the rotation mechanism and rotates along with the rotation of the rotation mechanism.

Optionally, the image quality compensation device further includes a lens base, and the lens base is located around the lens barrel.

Optionally, the rotating mechanism comprises a bearing, a rotating shaft, a driving gear and a motor, the motor is connected with the rotating shaft, the rotating shaft is connected with the driving gear, the driving gear is connected with the microscope base, and the bearing is connected with the microscope base.

Optionally, the force application mechanism is transversely embedded in the lens base, and the force application mechanism applies a transverse acting force to the lens barrel.

Optionally, the motor drives the rotating shaft to rotate, the rotating shaft drives the driving gear to rotate, and the driving gear drives the lens base, the lens barrel and the force application mechanism to rotate together.

Optionally, the force application mechanism is longitudinally embedded in the lens base, and applies a longitudinal acting force to the lens barrel.

Optionally, the force application mechanism is a force application mechanism with a universal coupling.

Optionally, the image quality compensation device includes a flexible block, and the flexible block is located below the lens barrel and bears the gravity of the lens.

Optionally, the motor drives the rotating shaft to rotate, the rotating shaft drives the driving gear to rotate, and the driving gear drives the lens base and the force application mechanism to rotate together.

The invention also provides an optical system, which comprises the image quality compensation device and is used for adjusting one aberration item group to realize image quality compensation, wherein the aberration item group comprises two aberration items with a certain rotation angle relationship.

Optionally, the number of the image quality compensation devices is several, and the several image quality compensation devices adjust a plurality of the aberration term groups.

The invention also provides a method for compensating the image quality of the photoetching projection objective, which comprises the following steps: the force application mechanism applies pressure to the lens cone to enable the lens in the lens cone to deform, and the rotation mechanism rotates to achieve image quality compensation.

The image quality compensation device and method and the optical system comprising the image quality compensation device can realize image quality compensation through rotation and deformation of the lens, can compensate various image qualities, reduce the difficulty of image quality compensation and reduce the cost.

Drawings

Fig. 1 is a structural diagram of an image quality compensation apparatus provided in embodiment 1 of the present invention;

fig. 2 is a cross-sectional view of an image quality compensation apparatus provided in embodiment 1 of the present invention;

FIG. 3 is a graph of a Zernike polynomial arrangement;

FIG. 4 is a plot of the fitted surface profile of Z6;

FIG. 5 is a plot of the fitted surface profile of Z6;

FIG. 6 is a block diagram of a lithographic projection objective;

fig. 7 is a structural diagram of an image quality compensation apparatus provided in embodiment 2 of the present invention;

fig. 8 is a cross-sectional view of an image quality compensation apparatus provided in embodiment 2 of the present invention;

fig. 9 is a schematic diagram of an optical system provided in embodiment 3 of the present invention;

FIG. 10 is a plot of the fitted surface profile of Z12;

FIG. 11 is a distribution diagram of the fitted surface profile of Z13

Reference numbers in the figures:

1-a first lens; 2-a second lens; 3-a third lens; 4-a fourth lens; 5-a fifth lens; 6-a movable lens; 8-a lens barrel; 9-a rotating mechanism; 10-a force application mechanism; 11-a bearing; 12-a rotating shaft; 13-a drive gear; 14-a motor; 15-a lens base; 16-a flexible block; 20-a light source; 21-mask plate; 22-an optical system; 23-silicon chip surface; 24-a first image quality compensation device; 25-second image quality compensation means.

Detailed Description

The image quality compensation device proposed by the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. Advantages and features of the present invention will become apparent from the following description and from the claims. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.

The existing image quality compensation scheme has the problems of single compensation, high difficulty and high cost, and the inventor of the application invents a novel image quality compensation device through long-term experiments and researches, so that the problems are solved.

The invention provides an image quality compensation device, which comprises a lens barrel, a force application mechanism and a rotating mechanism, wherein the lens barrel is positioned on the rotating mechanism and rotates along with the rotation of the rotating mechanism, the force application mechanism is positioned on the rotating mechanism and rotates along with the rotation of the rotating mechanism, and the force application mechanism applies pressure to the lens barrel to deform a lens in the lens barrel.

Example one

As shown in fig. 1, the image quality compensation device includes a lens barrel 8, a rotation mechanism 9 and a force application mechanism 10, the lens barrel contains a lens 7, the lens 7 is a movable lens, the lens barrel 8 is located on the rotation mechanism 9 and rotates along with the rotation of the rotation mechanism 9, the force application mechanism 10 applies pressure to the lens barrel 8 to deform the lens barrel 8, and the lens barrel further transmits the pressure to the lens 7 to deform the upper and lower surfaces of the lens 7.

Fig. 2 is a cross-sectional view of the image quality compensation device, please refer to fig. 2, the image quality compensation device further includes a lens holder 15, and the lens holder 15 is located around the lens 7. The rotating mechanism 9 includes a bearing 11, a rotating shaft 12, a driving gear 13 and a motor 14, and the rotating mechanism in this embodiment is a bearing-type rotating mechanism. The bearing 11 is connected with the mirror base 15, the motor 14 is connected with the rotating shaft 12, and the rotating shaft 12 is connected with the driving gear 13. The force application mechanism 10 is transversely embedded in the lens base 15 and connected with the lens barrel 8, the force application mechanism 10 applies transverse pressure (in the direction indicated by an arrow in the figure) to the lens barrel 8 to deform the lens 7, meanwhile, the motor 14 drives the rotating shaft 12 to rotate, the rotating shaft 12 drives the driving gear 13 to rotate, and then the lens base 15, the lens barrel 8 and the force application mechanism 10 rotate together, so that the stress surface type of the lens is changed and the lens rotates at the same time.

The principle of the device for image quality compensation provided by the invention is realized based on the mutual relation between image qualities, a Zernike polynomial can be used for fitting the surface shape of an optical element, and the change of the lens surface shape and the rotation of the lens are mainly carried out by utilizing the fixed relation of the two aberrations on the rotation angle. A zernike polynomial is a complete set of an infinite number of polynomials with two variables R and theta, where R denotes radius and theta denotes phase angle, and fig. 3 lists a portion of the zernike polynomials, and subsequently for convenience of representation Z1 denotes the formula in the first row, Z2 denotes the formula in the second row, and so on, and Z16 denotes the formula in row 16. Since zernike polynomials are common knowledge in the optical field, the meaning of each formula in a zernike polynomial is not described here, and since zernike polynomials are infinite in number, it is not possible to list them completely, fig. 3 is only representative of these 16-term polynomials, and it will be understood by those skilled in the art that other non-listed components are within the scope of the present invention. It should also be noted that the order of the zernike polynomials listed in the present disclosure is the order commonly used at present, but some other orders are not excluded, and those skilled in the art will understand that other orders of the zernike polynomials are also within the scope of the present disclosure.

Referring to fig. 4 and 5, fig. 4 is a fitting surface profile of Z5, fig. 5 is a surface profile of Z6, and comparing fig. 4 and 5 shows that Z5 and Z6 are different by 45 degrees of rotation angle. If the lens is designed with the surface type of Z5 only, but the effect of Z6 is more remarkable in practical application, the compensation of Z6 can be realized through the rotation and deformation of the lens.

Table 1 lists some angular relationships among zernike terms, fig. 6 shows a part of a lithographic projection objective, and during an actual lithographic projection exposure, the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, and the fifth lens 5 are all fixed lenses, the lens 7 is a movable lens, and the surface shape of the lens 7 can be changed, so as to realize image quality compensation. This embodiment only exemplifies one situation in the actual production process, and those skilled in the art can understand that the lens can be flexibly selected to compensate the image quality according to the actual requirement.

TABLE 1 angular relationship between Zernike terms

Zernike terms	By angle of difference
		Z5 and Z6	45°
Z7 and Z8	90°
		Z10 and Z11	30°
Z12 and Z13	45°
		…	…

Example two

Referring to fig. 7, the image quality compensation device includes a lens barrel 8, a rotation mechanism 9 and a force application mechanism 10, the lens barrel contains a lens 7, the lens barrel 8 is located on the rotation mechanism 9 and rotates along with the rotation of the rotation mechanism 9, the force application mechanism 10 is located on the rotation mechanism 9 and rotates while locking the rotation of the rotation mechanism 9, the force application mechanism 10 applies pressure to the lens barrel 8 to deform the lens barrel 8, and the lens barrel further transmits the pressure to the lens 7 to deform the upper and lower surfaces of the lens 7.

With continued reference to fig. 8, the image quality compensation device further includes a lens holder 15, and the lens holder 15 is located around the lens 7. The lens cone 8 is provided with a flexible block 16 below, and the flexible block 16 can bear the gravity of the lens 7. The rotating mechanism 9 includes a bearing 11, a rotating shaft 12, a driving gear 13 and a motor 14, and the rotating mechanism in this embodiment is a bearing-type rotating mechanism. The bearing 11 is connected with the mirror base 15, the motor 14 is connected with the rotating shaft 12, and the rotating shaft 12 is connected with the driving gear 13. The force applying mechanism 10 is longitudinally embedded in the lens base 15 and connected to the lens barrel 8, in this example, the force applying mechanism is preferably a force applying mechanism with a universal coupling, the force applying mechanism 10 applies a longitudinal pressure (in a method shown by an arrow in the figure) to the lens barrel 8 to stretch or squeeze the lens barrel 8, so as to deform the lens 7, and the flexible block can bear the gravity of the lens 7 to fix the lens at a certain position. Meanwhile, the motor 14 drives the rotating shaft 12 to rotate, the rotating shaft 12 drives the driving gear 13 to rotate, and then the lens base 15 and the force application mechanism 10 rotate together, so that a lens which is subjected to rotation and stress to generate specific deformation is generated, and finally image quality compensation is realized.

The present embodiment adopts the same principle as that adopted in embodiment 1, and redundant description is not given here.

EXAMPLE III

Correspondingly, the present invention further provides an optical system, where the optical system includes an image quality compensation device, the image quality compensation device adjusts an aberration term group to implement image quality compensation, the aberration term group includes two aberration terms or multiple aberration terms with a certain rotation angle relationship, and this embodiment takes two aberration terms as an example of an aberration term group for explanation. The image quality compensation device is the image quality compensation device provided in any one of the above embodiments. The phase difference term is any one of Zernike polynomials, such as Z5, Z6 or Z7. The phase difference item set is two phase difference items with certain angle relation, such as Z5 and Z6, Z12 and Z13, and the like. The operation of the optical system will be explained in detail below.

The optical system includes the image quality compensation devices, and can adjust the aberration term sets, referring to fig. 9, the optical system 22 includes a first image quality compensation device 24 and a second image quality compensation device 25, and the first image quality compensation device 24 and the second image quality compensation device 25 are disposed opposite to each other. The light emitted from the light source 20 enters the optical system 22 after passing through the mask 21, and the first compensation device 24 and the second compensation device 25 can rotate in the same direction or relative to each other to perform combined image quality compensation, so as to simultaneously compensate for four image qualities.

In the zernike polynomials, the phase difference terms Z5, Z6, Z12 and Z13 are all astigmatic terms, wherein Z5, Z6 are low order aberrations. The formula and meaning of Z1-Z16 in FIG. 3 show that: z5 and Z12 are symmetrically distributed in the 0 ° or 90 ° direction, and Z6 and Z13 are symmetrically distributed in the ± 45 ° direction. When the lens profile is brought to Z5 by applying a force to the lens, a certain magnitude of Z12 is also brought about. As shown in Table 2, the simulation data shows that when 1.0393nm of Z5 is generated for the amount of lens surface shape deformation obtained when the driving force for generating Z5 distribution is 100N, 0.0777nm of Z12 is generated. When the magnitude of the compensation Z5 is large, the influence of Z12 needs to be considered, at this time, if two lenses are used as compensation mechanisms, the two lenses can cancel each other, and at the same time, the image quality compensation device can compensate Z6 and Z13 by rotating, that is, the two image quality compensation devices can compensate four image qualities, the phase difference items Z5 and Z6 form a phase difference item group, and the phase difference items Z12 and Z13 form a phase difference item group. FIG. 10 is a map profile of Z12 and FIG. 11 is a map profile of Z13, both of which may be interchanged by a 45 rotation of the lens.

TABLE 2 simulation data

	Front surface (nm)	Rear surface (nm)
			Z5	1.0393	1.0407
Z6	0.0191	0.0192
			Z7	-0.0001	-0.0002
Z8	0.0001	0.0001
			Z9	0	0
Z10	-0.0048	-0.0048
			Z11	0.0083	0.0084
Z12	0.0777	0.0775
			Z13	0.0016	0.0016

The above embodiments take two image quality compensation devices as an example, and those skilled in the art will understand that an optical system including other numbers of image quality compensation devices is also within the scope of the present invention. And the optical system of the image quality compensation device for other different lens group pairs with certain corresponding rotation angles is also within the protection scope of the invention.

Correspondingly, the invention also provides a method for compensating the image quality of the photoetching projection objective, which comprises the following steps: the force application mechanism applies pressure to the lens cone to enable the lens in the lens cone to deform, and then the rotation mechanism rotates to achieve image quality compensation. The force applying mechanism, the lens barrel, the lens and the rotating mechanism are the force applying mechanism, the lens barrel, the lens and the rotating mechanism in any one of the above embodiments.

The method of compensating image quality employs a Zernike polynomial that fits the face shape of the lens. The method of image quality compensation will be specifically described below with reference to example 1.

Referring to fig. 2, the rotating mechanism 9 includes a bearing 11, a rotating shaft 12, a driving gear 13 and a motor 14, and the rotating mechanism in this embodiment is a bearing-type rotating mechanism. The bearing 11 is connected with the mirror base 15, the motor 14 is connected with the rotating shaft 12, and the rotating shaft 12 is connected with the driving gear 13. The force application mechanism 10 is transversely embedded in the lens base 15 and connected with the lens barrel 8, the force application mechanism 10 applies transverse pressure (in the direction indicated by an arrow in the figure) to the lens barrel 8 to deform the lens 7, meanwhile, the motor 14 drives the rotating shaft 12 to rotate, the rotating shaft 12 drives the driving gear 13 to rotate, and then the lens base 15, the lens barrel 8 and the force application mechanism 10 rotate together, so that the stress surface type of the lens is changed while the lens is rotated, and the purpose of compensating the image quality is finally achieved.

The principle of the image quality compensation method provided by the invention is realized based on the mutual relation between image qualities, a Zernike polynomial can be used for fitting the surface shape of an optical element, and the change of the lens surface shape and the rotation of the lens are mainly carried out by utilizing the fixed relation of the two aberrations on the rotation angle. A zernike polynomial is a complete set of an infinite number of polynomials with two variables R and theta, where R denotes radius and theta denotes phase angle, and fig. 3 lists a portion of the zernike polynomials, and subsequently for convenience of representation Z1 denotes the formula in the first row, Z2 denotes the formula in the second row, and so on, and Z16 denotes the formula in row 16. Since zernike polynomials are common knowledge in the optical field, the meaning of each formula in a zernike polynomial is not described here, and since zernike polynomials are infinite in number, it is not possible to list them completely, fig. 3 is only representative of these 16-term polynomials, and it will be understood by those skilled in the art that other non-listed components are within the scope of the present invention. It should also be noted that the order of the zernike polynomials listed in the present disclosure is the order commonly used at present, but some other orders are not excluded, and those skilled in the art will understand that other orders of the zernike polynomials are also within the scope of the present disclosure.

In summary, the image quality compensation device and method and the optical system including the image quality compensation device provided by the invention can realize image quality compensation through rotation and deformation of the lens, and can compensate various image qualities, thereby reducing difficulty of image quality compensation and reducing cost.

The above description is only for the purpose of describing the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention, and any variations and modifications made by those skilled in the art based on the above disclosure are within the scope of the appended claims.

Claims

1. The utility model provides an image quality compensation device, its characterized in that includes lens cone, application of force mechanism and rotary mechanism, application of force mechanism to the lens cone exerts pressure, makes lens in the lens cone produce deformation, the lens cone is located rotary mechanism, the lens in the lens cone rotates along with rotary mechanism's rotation when producing deformation to adjust an aberration item group, aberration item group is two kinds of aberration items or multiple aberration items that have certain rotation angle relation, wherein, rotary mechanism includes the rotation axis, the rotation axis drives the lens cone is rotatory along the Rz direction.

2. The image quality compensation apparatus of claim 1, wherein the force application mechanism is located on the rotation mechanism and rotates with rotation of the rotation mechanism.

3. The image quality compensation device of claim 1, further comprising a lens mount located around the lens barrel.

4. The image quality compensation device of claim 3, wherein the rotation mechanism further comprises a bearing, a driving gear and a motor, the motor is connected with the rotation shaft, the rotation shaft is connected with the driving gear, the driving gear is connected with the mirror base, and the bearing is connected with the mirror base.

5. The image quality compensation device of claim 4, wherein the force application mechanism is laterally embedded in the lens holder, and the force application mechanism applies a lateral force to the lens barrel.

6. The image quality compensation device of claim 5, wherein the motor drives a rotation shaft to rotate, the rotation shaft drives the driving gear to rotate, and the driving gear drives the lens base, the lens barrel and the force application mechanism to rotate together.

7. The image quality compensation device of claim 4, wherein the force application mechanism is longitudinally embedded in the lens holder, and applies a longitudinal force to the lens barrel.

8. The image quality compensation apparatus of claim 7, wherein the force applying mechanism is a force applying mechanism with a universal joint.

9. The image quality compensation device of claim 8, wherein the image quality compensation device comprises a flexible block, the flexible block is located below the lens barrel and bears the gravity of the lens.

10. The image quality compensation apparatus of claim 9, wherein the motor drives a rotation shaft, the rotation shaft drives the driving gear to rotate, and the driving gear drives the lens holder and the force application mechanism to rotate together.

11. An optical system comprising the image quality compensation device of any one of claims 1-10, wherein the image quality compensation device is a plurality of image quality compensation devices, and the plurality of image quality compensation devices adjust a plurality of sets of aberration terms.

12. A method of compensating the image quality of a lithographic projection objective using an image quality compensation apparatus according to any one of claims 1 to 10, comprising: the force application mechanism applies pressure to the lens cone to enable the lens in the lens cone to deform, and the rotation mechanism rotates to achieve image quality compensation.