阅读说明：本技术 一种复眼照明系统的匹配方法 (Matching method of compound eye lighting system ) 是由 徐乐 王丽萍 吴越 张旭 于 2021-07-15 设计创作，主要内容包括：本发明提供一种复眼照明系统的匹配方法,包括配置有光阑复眼的光阑复眼基板和配置有视场复眼的视场复眼基板,包括：获取每种照明模式下可用光阑复眼的位置,获取所述可用光阑复眼与视场复眼的最优组合,以及获得所述最优组合时所述可用光阑复眼的初始角；对当所述可用光阑复眼与视场复眼为最优组合时被重复组合所述可用光阑复眼进行重新放置,并使无法放置的光阑复眼所匹配的视场复眼通过转动偏离照明光路,使其不参与重复的照明模式,进而获得所述可用光阑复眼与视场复眼的最终组合。通过本公开的优化匹配方法,可以获得可用光阑复眼与视场复眼的最佳组合,该使得入射到掩膜版上的EUV光有相对最高的能量利用率和照明均匀性。(The invention provides a matching method of a compound eye lighting system, which comprises a diaphragm compound eye substrate provided with a diaphragm compound eye and a field compound eye substrate provided with a field compound eye, and comprises the following steps: acquiring the position of an available diaphragm compound eye in each illumination mode, acquiring an optimal combination of the available diaphragm compound eye and a field compound eye, and acquiring an initial angle of the available diaphragm compound eye in the optimal combination; and when the available diaphragm compound eye and the field compound eye are in the optimal combination, the available diaphragm compound eye is repeatedly combined and placed again, and the field compound eye matched with the diaphragm compound eye which cannot be placed deviates from an illumination light path through rotation, so that the field compound eye does not participate in a repeated illumination mode, and further the final combination of the available diaphragm compound eye and the field compound eye is obtained. By the optimized matching method disclosed by the disclosure, the optimal combination of the available diaphragm compound eye and the field-of-view compound eye can be obtained, so that EUV light incident on the mask has relatively highest energy utilization rate and illumination uniformity.)

1. A matching method of a compound eye illumination system, including a diaphragm compound eye substrate provided with a diaphragm compound eye and a field compound eye substrate provided with a field compound eye, comprising:

acquiring the position of an available diaphragm compound eye in each illumination mode, wherein the available diaphragm compound eye can be matched with a field compound eye, so that incident light can enter a mask and form illumination;

acquiring an optimal combination of the available diaphragm compound eye and the field-of-view compound eye, and acquiring an initial angle of the available diaphragm compound eye in the optimal combination; when the optimal combination enables a plurality of illumination modes to coexist, the sum of included angles formed by the incident direction of incident light of the illumination modes incident on the mask and the normal direction of the mask is minimum;

and repositioning the available diaphragm compound eye which is repeatedly combined when the available diaphragm compound eye and the field compound eye are in the optimal combination to obtain the final combination of the available diaphragm compound eye and the field compound eye.

2. The matching method according to claim 1, further comprising: and acquiring the positions of the diaphragm compound eyes available in each illumination mode by a parting method.

3. The matching method according to claim 2, wherein the specific method for acquiring the position of the diaphragm compound eye available in each illumination mode comprises:

determining a scaling factor for each illumination mode according to the coherence factor;

scaling the shape formed by the illumination mode by a range of coherence factors;

when the coincidence frequency of the PF matrix and the fractal matrix is odd, the complex eye of the diaphragm at the position is assigned to be 1, and when the coincidence frequency is even, the complex eye of the diaphragm at the position is assigned to be 0;

and finishing the typing when the number of the diaphragm compound eyes with the value of 1 is the same as that of the field compound eyes.

4. The matching method according to claim 1, wherein the optimal combination of the available diaphragm compound eyes and field of view compound eyes is obtained by Hungarian algorithm.

5. The matching method according to claim 4, wherein the specific method for obtaining the optimal combination of the available diaphragm compound eye and the field of view compound eye comprises:

-performing a one-to-one matching of the available diaphragm compound eye and field of view compound eye in each illumination mode;

solving the matching result of the available diaphragm compound eye and the field of view compound eye in multiple illumination modes under the condition that the sum of included angles between the incident direction of incident light incident on the mask plate and the normal direction of the mask plate is minimum;

-obtaining an optimal combination of said available diaphragm compound eye and field compound eye and an initial angle of said available diaphragm compound eye at the time.

6. The matching method according to claim 1, wherein the available diaphragm compound eyes which are repeatedly combined are repositioned by a loop push algorithm, and the field compound eyes matched with the diaphragm compound eyes which cannot be repositioned are rotated away from the illumination light path so as not to participate in the repeated illumination mode.

7. The matching method according to claim 6, wherein the specific method for repositioning the repeatedly combined available diaphragm compound eye comprises:

-constructing a matrix mask with said available diaphragm compound eyes in all said illumination modes and, all said illumination modes;

marking the diaphragm compound eye corresponding to the unique illumination mode as a non-multiplexing diaphragm compound eye, and marking the same diaphragm compound eye corresponding to at least two illumination modes as a multiplexing diaphragm compound eye;

-obtaining a final combination of said available diaphragm compound eye and field of view compound eye by a cyclic push algorithm.

Technical Field

The invention relates to the technical field of photoetching, in particular to a matching method of a compound eye lighting system.

Background

Extreme Ultraviolet Lithography (EUVL) is a projection Lithography technique that uses Extreme Ultraviolet light with a wavelength of 13.5nm as the operating wavelength. According to Rayleigh criterion, the extreme ultraviolet lithography technology can be used to obtain smaller exposure system resolution, so that EUV becomes the first choice technology for realizing the industrialization of the technical node integrated circuit of 7nm and below.

In order to meet the illumination requirements of optimal lithographic resolution of different reticles, the prior art provides a double-row compound eye optical design. In the scheme, the uniformity of the system on the mask surface can be optimized by selecting the diaphragm compound eye and adjusting the matching of the field compound eye and the diaphragm compound eye, so that the method for matching the diaphragm compound eye and the field compound eye of the field compound eye becomes the key technology of the extreme ultraviolet lithography illumination system.

Disclosure of Invention

Therefore, an object of the present invention is to provide a matching method of a compound eye illumination system in view of the above problems.

According to a first aspect of the present disclosure, there is provided a matching method of a compound eye illumination system, including a diaphragm compound eye substrate configured with a diaphragm compound eye and a field compound eye substrate configured with a field compound eye, the method including:

acquiring the position of an available diaphragm compound eye in each illumination mode, wherein the available diaphragm compound eye can be matched with a field compound eye, so that incident light can enter a mask and form illumination;

acquiring an optimal combination of the available diaphragm compound eye and the field-of-view compound eye, and acquiring an initial angle of the available diaphragm compound eye in the optimal combination; when the optimal combination enables a plurality of illumination modes to coexist, the sum of included angles formed by the incident direction of incident light of the illumination modes incident on the mask and the normal direction of the mask is minimum;

and repeatedly combining the available diaphragm compound eye and the field compound eye when the available diaphragm compound eye and the field compound eye are in the optimal combination, and repositioning to obtain the final combination of the available diaphragm compound eye and the field compound eye.

And for the field-of-view compound eye matched with the diaphragm compound eye which cannot be placed, the field-of-view compound eye deviates from an illumination light path through rotation, so that the field-of-view compound eye does not participate in a repeated illumination mode.

In some possible implementations, the method further includes: and acquiring the positions of the diaphragm compound eyes available in each illumination mode by a parting method.

In some possible implementations, the specific method for acquiring the position of the diaphragm compound eye available in each illumination mode includes:

determining a scaling factor for each illumination mode according to the coherence factor;

scaling the shape formed by the illumination mode by a range of coherence factors;

when the coincidence frequency of the PF matrix and the fractal matrix is odd, the complex eye of the diaphragm at the position is assigned to be 1, and when the coincidence frequency is even, the complex eye of the diaphragm at the position is assigned to be 0;

and finishing the typing when the number of the diaphragm compound eyes with the value of 1 is the same as that of the field compound eyes.

In some possible implementation manners, the optimal combination of the available diaphragm compound eyes and the field of view compound eyes is obtained through Hungarian algorithm.

In some possible implementations, the specific method for obtaining the optimal combination of the available diaphragm compound eye and the field of view compound eye includes:

-performing a one-to-one matching of the available diaphragm compound eye and field of view compound eye in each illumination mode;

solving the matching result of the available diaphragm compound eye and the field of view compound eye in multiple illumination modes under the condition that the sum of included angles between the incident direction of incident light incident on the mask plate and the normal direction of the mask plate is minimum;

-obtaining an optimal combination of said available diaphragm compound eye and field compound eye and an initial angle of said available diaphragm compound eye at the time.

In some possible implementation manners, the available diaphragm compound eyes which are repeatedly combined are relocated through a loop stack-pushing algorithm, and the field-of-view compound eyes matched with the diaphragm compound eyes which cannot be relocated deviate from an illumination light path through rotation, so that the field-of-view compound eyes do not participate in illumination of repeated illumination modes.

In some possible implementations, the specific method for repeatedly repositioning the available diaphragm compound eyes in combination and enabling the field-of-view compound eyes matched with the diaphragm compound eyes which cannot be repositioned to not participate in the repeated illumination mode includes:

-constructing a matrix mask with said available diaphragm compound eyes in all said illumination modes and, all said illumination modes;

marking the diaphragm compound eye corresponding to the unique illumination mode as a non-multiplexing diaphragm compound eye, and marking the same diaphragm compound eye corresponding to at least two illumination modes as a multiplexing diaphragm compound eye;

-obtaining a final combination of said available diaphragm compound eye and field of view compound eye by a cyclic push algorithm.

The matching method of the present disclosure has at least the following advantages: by the optimized matching method disclosed by the disclosure, the optimal combination of the available diaphragm compound eye and the field-of-view compound eye can be obtained, so that EUV light incident on the mask has relatively highest energy utilization rate and illumination uniformity.

The results of the embodiments of the disclosure obtained after light ray tracing simulation show that, with the method of the disclosure, the EUV light is illuminated on the ground surface with uniformity of less than 1% in each illumination mode, which completely meets the uniformity requirement of the EUV illumination system.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

Fig. 1 shows a flowchart of a method for matching a field of view compound eye with a diaphragm compound eye in a compound eye illumination system according to an embodiment of the present disclosure;

fig. 2 shows an embodiment of the present disclosure, which obtains diaphragm compound eye distribution respectively selected under four illumination modes through fractal;

FIG. 3 shows the compound eye distribution of all diaphragms selected by four illumination modes obtained by fractal in one embodiment of the present disclosure;

FIG. 4 shows a flow diagram of selecting illumination patterns by a fractal method in one embodiment of the present disclosure;

FIG. 5 illustrates the generation rules of a matrix mask in one embodiment of the present disclosure;

FIG. 6 shows a flow diagram of a loop push algorithm in one embodiment of the present disclosure;

FIG. 7 shows illumination uniformity verification results on the polished side after simulation by LightTools in one embodiment of the present disclosure.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings of the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

The prior art discloses an illumination system, which reflects light beams through double rows of compound eyes (field compound eyes and diaphragm compound eyes) and then reflects the light beams through a double relay mirror to enter a mask plate to form illumination. In the lighting system, for the purpose of engineering realizability, the field compound eye lens is provided with a reflecting mirror which can rotate in a plane, the reflecting surface has a specific curvature radius and the mirror body is arc-shaped; and the diaphragm compound eye lens is configured as a fixed non-rotatable plane mirror which can only have an initial rotation angle.

After the illumination system is determined, the number of the field compound eyes and the diaphragm compound eyes is also determined. The adjustment method based on the lighting system is therefore: the emitted EUV light firstly enters a visual field compound eye substrate, and each visual field compound eye on the visual field compound eye substrate is adjusted to rotate in the plane where the visual field compound eye is located; EUV light is reflected to a specific diaphragm compound eye on the diaphragm compound eye substrate through the field compound eye to form matching, and only reflected light of the diaphragm compound eye matched with the field compound eye can be finally incident on the mask plate to form illumination.

The inventor considers that the key factor influencing the illumination uniformity of the EUV light on the mask surface in the system is the included angle between the incident direction of the EUV light and the normal direction of the mask when the EUV light is incident on the mask after being reflected by the field compound eye and the diaphragm compound eye in sequence. The smaller the angle, the higher the energy utilization and illumination uniformity of the light incident on the reticle. In practical application, a plurality of beams of EUV light reflected by different combinations of the field compound eye and the diaphragm compound eye are incident to the mask plate for illumination, so that the effect of reducing the included angle between the incident direction of the EUV light and the normal direction of the mask plate on the whole can be achieved by reasonably configuring the field compound eye and the diaphragm compound eye by optimizing the combination of the field compound eye and the diaphragm compound eye, and further the EUV light incident on the mask plate has relatively highest energy utilization rate and illumination uniformity.

Specifically, the present disclosure provides a matching method of a compound eye illumination system, having a diaphragm compound eye substrate configured with a diaphragm compound eye and a field compound eye substrate configured with a field compound eye, the matching method specifically including (refer to fig. 1):

s1, acquiring the position of an available diaphragm compound eye in each illumination mode, wherein the available diaphragm compound eye can be matched with a field compound eye, so that incident light can enter a mask and form illumination;

s2, acquiring an optimal combination of the available diaphragm compound eye and the field compound eye, and acquiring an initial angle of the available diaphragm compound eye when the optimal combination is acquired; when the optimal combination enables a plurality of illumination modes to coexist, the sum of included angles formed by the incident direction of incident light of the illumination modes incident on the mask and the normal direction of the mask is minimum;

s3, when the available diaphragm compound eye and the field compound eye are in the optimal combination, the available diaphragm compound eye is repeatedly combined and placed again, the field compound eye matched with the diaphragm compound eye which cannot be placed deviates from the illumination light path through rotation, so that the field compound eye does not participate in the repeated illumination mode, and the final combination of the available diaphragm compound eye and the field compound eye is obtained.

For S1, the position of the available diaphragm compound eye in each illumination mode is obtained, and the available diaphragm compound eye and the field compound eye are matched with each other, so that the incident light can enter the mask and form illumination.

The illumination mode refers to that diaphragm compound eyes positioned at different positions are selected on the diaphragm compound eye substrate, and the selected diaphragm compound eyes can form different shapes on the diaphragm compound eye substrate from the distribution of the diaphragm compound eyes on the diaphragm compound eye substrate. Since each illumination mode is given a coherence factor epsilon according to the lithography requirements, the coherence factor epsilon limits the range of diaphragm compound eyes that can be chosen.

In one embodiment, each compound aperture on the compound aperture substrate is abstracted into elements of a matrix, and elements at different positions of the matrix are selected, namely different compound apertures are selected, so that different illumination modes are formed. In this embodiment, the different illumination modes Z are obtained by means of a typing method_i(i∈[1,4]) And the selected diaphragm compound eye set (PF) in the lighting mode_i(first diaphragm compound eye set). The details are as follows (fig. 2):

setting the value of the selected position element as 1 and the value of the unselected position element as 0;

determining the scaling factor p ═ p for each illumination mode by the coherence factor ε₀；

Scaling the shape of the illumination mode in equal proportion within the range of the coherence factor epsilon, wherein the proportion coefficient is p;

if p > ε, then end; if the coincidence frequency of the light stop compound eye matrix and the fractal matrix in the range of the coherence factor epsilon is odd, the element value of the position is 1, and if the coincidence frequency is even, the element value of the position is 0;

if the number of 1 element is the same as the number of FF, the process is ended.

The distribution of the diaphragm compound eyes selected under different illumination modes can be obtained by a parting method, as shown in fig. 3. In the figure, the image 1 is the diaphragm compound eye distribution used in the circular illumination mode, the image 2 is the diaphragm compound eye distribution used in the annular illumination mode, the image 3 is the diaphragm compound eye distribution used in the secondary illumination mode, and the image 4 is the diaphragm compound eye distribution used in the quaternary illumination mode. Different illumination modes have different diaphragm compound eyes due to different selection, so that different distribution images are formed, namely different position information represented by the diaphragm compound eyes on the diaphragm compound eye substrate. Fig. 3 illustrates four illumination modes as an example, and does not limit the disclosure in any way.

For S2, obtaining an optimal combination of the available diaphragm compound eye set and the field of view compound eye, and obtaining an initial angle of the available diaphragm compound eye at the optimal combination; and when the optimal combination enables a plurality of illumination modes to coexist, the sum of included angles formed by the incident direction of incident light of the illumination modes incident on the mask and the normal direction of the mask is minimum.

After the coherence factor is given, the distribution of the diaphragm compound eyes available in each illumination mode can be obtained through a fractal algorithm. For any one illumination mode, the fractal mode can obtain various solutions in the range of coherence factors, namely various diaphragm compound eye selection distributions meeting the conditions.

And when EUV light is reflected by the field compound eye and the diaphragm compound eye in sequence and then enters the mask plate, the smaller the included angle between the incident direction and the normal direction of the mask plate is, the higher the energy utilization rate and the illumination uniformity of the EUV light entering the mask plate are. Therefore, the included angle alpha between the incident direction of the incident light and the normal direction of the mask is used_n，mAs a matching element as a matching condition, each field compound eye and the available diaphragm compound eye are paired one to one, and the included angle alpha is formed in multiple illumination modes_n，mAnd the minimum sum is used as an evaluation standard to obtain the matching combination of the field compound eye and the diaphragm compound eye of the optimal solution. At the same time, the included angle alpha is obtained_n，mThe initial angle of the eye is compounded by the available diaphragm. The method comprises the following specific steps:

the set formed by all the visual field compound eyes is recorded as { FF }, the number of { FF } elements is set as M, and each element (namely the visual field compound eye) in { FF } is numberedThe available diaphragm compound eyes are collected { PF }_iAll elements in (i.e., compound eyes of the diaphragm) are also numbered.

To fly across an arbitrary field of view (e.g., FF)_m) The reflected incident light strikes a diaphragm compound eye (such as PF)_n) Upper (M, n ∈ [1, M)]) Then the reflected light is incident to the mask plate, and the included angle between the incident direction and the normal direction of the mask plate is alpha_n，mAs a matching element.

With matching element α in all illumination modes_n，mConstructing a field compound eye-diaphragm compound eye matching element matrix, carrying out one-to-one pairing on each field compound eye element (represented position information) and available diaphragm compound eye elements (represented position information), and taking the sum alpha of all pairing results_n，mThe smallest is the optimal solution.

Meanwhile, the initial angle set { alpha } and { beta } of the available diaphragm compound eye are obtained through the matching result.

As shown in fig. 4, the distribution of all diaphragm compound eyes in four illumination modes is calculated by fractal, wherein different amplitudes are marked with different colors to indicate that a specific one is used by several illumination modes. Wherein, the diaphragm compound eye with the highest amplitude is the optimal solution under the four illumination modes.

For S3, repositioning the available diaphragm compound eye which is repeatedly combined when the available diaphragm compound eye and the field of view compound eye are in the optimal combination, and obtaining a final combination of the available diaphragm compound eye and the field of view compound eye.

Defining all available diaphragm compound eyes in the multiple illumination modes obtained by the processing steps as a set { PF }, and defining the optimal matching combination of the field-of-view compound eye and the diaphragm compound eye as follows: { Z_i{(FF_m-FF_n)}}。

And constructing a matrix mask by using the available diaphragm compound eye set { PF } as a row and the illumination mode as a column. Wherein, 1 in the matrix represents that the mode uses the available diaphragm compound eye lens of the corresponding row, 0 represents that the mode is not used, and whether each element in the matrix is 1 or 0 can be determined according to the available diaphragm compound eye set { PF }_iAnd (4) determining.

The mask matrix satisfies the following conditions:

each row has at least one 1;

the sum of elements in each row is less than or equal to the number of lighting patterns;

the sum of each column is M, i.e. the same number as FF.

If each row only has one element 1, the PF corresponding to the row is called as 'non-multiplexing' PF;

if the number of the elements in each row 1 is greater than 1, the PF corresponding to the row is called a 'multiplexing' PF;

the position where the element is 1 is called a "placement point".

And placing the elements in the visual field compound eye set { FF } into the positions of the elements 1 in the matrix mask through a circular stack pushing algorithm. The rules of placement are as follows:

each element of 1 can only put no more than 1 FF;

the position of each element of 0 is not put into FF;

no duplicate FF is present in each column;

each row must be the same FF (the matrix mask is shown in fig. 5).

The specific loop push algorithm is as follows (see fig. 6):

s301, according to { Z_i{ (FFm-FFn) } } scheme places FFs in the mask matrix. i is 1, W is M, j is 1;

s302, order Z_i+1Z for a column element of 1 and a row in which the element is located_iFF number and Z in all "Placement points" in the row of locations where column is also 1_iThe columns are the same;

s303, deleting Z_i+1Having the same number of FFs therein. If i is 5, go to step S304; otherwise, go to step S302;

s304, order Z₁Z for a column element of 1 and a row in which the element is located₄FF number and Z in all "Placement points" in the row of locations where column is also 1₄The columns are identical. Deletion of Z₁Having the same number of FFs therein. To obtain Z₁Set of FFs { FF } not placed in a column_noThe number of elements is W. If W is 0, the process ends, otherwise, the process goes to step S305;

s305. will { FF }_noSerial number of all elements in+ j, put in the stack, j ═ j + 1. The element with the largest number needs to be changed into the first element of the stack, and a loop is formed. If j>M is finished, otherwise, the step S302 is carried out.

By the method, the matching mode of the available diaphragm compound eye { PF } and the field-of-view compound eye { FF } in all the illumination modes and the initial angle of the corresponding available diaphragm compound eye in the matching mode can be determined.

After the above processing, the matching method of the present embodiment is detected, and the lighting uniformity of the four lighting modes obtained by performing ray tracing simulation through LightTools software on the polished surface is less than 1%, which completely meets the uniformity requirement of the EUV lighting system (fig. 7).

While the invention has been illustrated and described in further detail by preferred embodiments, the invention is not limited to the disclosed examples and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.