CN102269926B - Method for optimizing optical proximity correction (OPC) of nonideal photoetching system based on Abbe vector imaging model - Google Patents

Abstract

The invention provides a method for optimizing optical proximity correction (OPC) of a nonideal photoetching system based on an Abbe vector imaging model. The method comprises the following steps of: setting transmittivity of an opening part and a light blocking part in a mask; setting a variable matrix Omega; setting a target function D as linear combination of an imaging evaluation function of an ideal image surface and an imaging evaluation function of an image surface of which the defocusing quantity is fnm; and guiding optimization on a mask pattern by using the variable matrix Omega and the target function D. By using the vector imaging model and taking vector characteristic of an electromagnetic field into consideration during acquisition of a space image, the optimized mask is suitable for the photoetching system with small numerical aperture (NA) and also suitable for the photoetching system of which the NA is more than 0.6. By the method, the gradient information of optimizing the target function is utilized and a steepest descent method is combined to optimize the pattern and the phase of an attenuated phase-shifting mask, so the optimization efficiency is high.

Description

Optimization method based on the imperfect etching system OPC of Abbe vector imaging model

Technical field

The present invention relates to the optimization method of a kind of imperfect etching system OPC (photoetching near-correction) based on Abbe (Abbe) vector imaging model, belong to photoetching resolution enhancement techniques field.

Background technology

Current large scale integrated circuit generally adopts etching system manufacturing.Etching system mainly is divided into: four parts such as illuminator (comprising light source and condenser), mask, optical projection system and wafer.The light that light source sends is incident to mask, the opening portion printing opacity of mask after focusing on through condenser; Through behind the mask, light is incident on the wafer that scribbles photoresist via optical projection system, and mask pattern just is replicated on the wafer like this.

The etching system of main flow is the ArF degree of depth ultraviolet photolithographic system of 193nm at present, and along with the photoetching technique node gets into 45nm-22nm, the critical size of circuit has been far smaller than the wavelength of light source.Therefore interference of light and diffraction phenomena are more remarkable, cause optical patterning to produce distortion and fuzzy.Etching system must adopt RET for this reason, in order to improve image quality.Optical proximity correction (optical proximity correction OPC) is a kind of important photoetching resolution enhancement techniques.The method of OPC through changing mask pattern and on mask, adding tiny auxiliary pattern reaches the purpose that improves optical patterning resolution.

In order further to improve the etching system imaging resolution, industry generally adopts immersion lithographic system at present.Immersion lithographic system enlarges numerical aperture (numerical aperture NA) between the lower surface of last lens of projection objective and wafer, having added refractive index greater than 1 liquid thereby reach, and improves the purpose of imaging resolution.Because immersion lithographic system has the characteristic of high NA (NA＞1), and when NA＞0.6, the scalar imaging model of etching system is no longer suitable.In order to obtain the imaging characteristic of accurate immersion lithographic system, must adopt OPC technology based on the vector imaging model, the mask in the immersion lithographic system is optimized.

In the actual light etching system, there is the kinds of processes changing factor.On the one hand; Because factors such as processing, debug causes optical projection system to produce certain influence to the phase place of incident light; And then influence the image quality of etching system; Make that etching system is nonideal etching system, this influence is mainly reflected in scalar aberration and two aspects of Polarization aberration of optical projection system.On the other hand; Because the influence of factors such as control; The physical location of wafer can change in the etching system, and then causes actual image planes position (wafer position) to depart from the position of the desirable image planes of etching system, and the phenomenon that this image planes depart from is presented as the image planes out of focus of etching system.The aerial image quality that on actual image planes position, obtains is compared with the aerial image quality that desirable image planes place obtains has bigger difference.In order to design the OPC prioritization scheme that is applicable to the actual light etching system, must consider the influence of kinds of processes changing factor in the etching system.

Pertinent literature (Journal of Optics, 2010,12:045601) to the partial coherence imaging system, a kind of OPC optimization method of the expansion etching system depth of focus based on gradient has been proposed.But said method has the deficiency of following two aspects: the first, and therefore above method is not suitable for the etching system of high NA based on the scalar imaging model of etching system.The second, above method is not considered the influence that scalar aberration, Polarization aberration of etching system etc. brought, thereby is not suitable for imperfect etching system.

Summary of the invention

The optimization method that the purpose of this invention is to provide a kind of imperfect etching system OPC based on Abbe vector imaging model.This method adopts the OPC technology of vector model that mask is optimized, and it is applicable to immersion lithographic system with high NA and dry lithography system with low NA.

Realize that technical scheme of the present invention is following:

The optimization method of a kind of imperfect etching system OPC based on Abbe vector imaging model, concrete steps are:

Step 101, mask pattern M is initialized as size is the targeted graphical of N * N ;

Step 102, the transmissivity that initial mask pattern M upper shed part is set are 1, and the transmissivity in resistance light zone is 0; Set the matrix of variables Ω of N * N: as M (x; O'clock y)=1;

is as M (x; O'clock y)=0;

be M (x, y) transmissivity of each pixel on the expression mask pattern wherein;

Step 103, objective function D is configured to the imaging evaluation function D at desirable image planes place ₁With defocusing amount be the imaging evaluation function D at f image planes place ₂Linear combination, i.e. D=η D ₁+ (1-η) D ₂, wherein η ∈ (0,1) is a weighting coefficient;

Imaging evaluation function D ₁Be set at aerial image and the Euler's distance between the targeted graphical behind the amplitude modulation(PAM) on the desirable image planes square, promptly

Wherein

Be the pixel value of targeted graphical, I _Nom(x is the pixel value of the aerial image on the corresponding desirable image planes of current mask y), and ω ∈ (0,1) is an amplitude modulation coefficient;

Imaging evaluation function D ₂Be set at defocusing amount and be aerial image and the Euler's distance between the targeted graphical behind the amplitude modulation(PAM) on the f image planes square, promptly

I wherein _Off(x is the pixel value of the aerial image on the f image planes for the corresponding defocusing amount of current mask y);

Step 104, calculating target function D are for the gradient matrix

of matrix of variables Ω

Step 105, utilize steepest prompt drop method to upgrade matrix of variables to be Ω '; Promptly

wherein s be predefined optimization step-length, obtain the mask pattern

of corresponding current Ω '

Step 106, calculate the corresponding target function value D of current mask pattern

; When D reaches predetermined upper limit value less than predetermined threshold or the number of times that upgrades matrix of variables Ω, get into step 107, matrix of variables Ω is that Ω ' returns step 104 otherwise make;

Step 107; Stop to optimize, and be targeted graphical horizontal direction cycle and the smaller of vertical direction in the cycle with the length of side of the said square window of core

of the current mask pattern of square window intercepting

;

Step 108; To

in the horizontal direction with the enterprising line period property continuation of vertical direction; Mask size after continuation is decided to be the figure

that obtains this moment through the mask pattern after optimizing more than or equal to the targeted graphical size.

In the step 103 according to the invention, aerial image on the desirable image planes of current mask correspondence and the corresponding defocusing amount of current mask are that the acquisition process of the aerial image on the f image planes is:

Step 201, mask pattern M grid is turned to N * N sub regions;

Step 202, surface of light source is tiled into a plurality of pointolites, with each grid region center point coordinate (x _s, y _s) represent the pairing pointolite coordinate of this grid region;

Step 203, according to required obtain residing image planes of aerial image and desirable image planes apart from δ, obtain the variable quantity ξ of the etching system incident light phase place that causes by said δ; Wherein to the aerial image on the desirable image planes, then δ=0 is the aerial image on the f image planes, then δ=f to defocusing amount;

Step 204, obtain the scalar aberration matrix W of describing optical projection system scalar aberration (α '; β ') and describe the Polarization aberration matrix J (α ', β ') of optical projection system Polarization aberration, wherein (α '; β ', γ ') be that global coordinate system carries out the coordinate system behind the Fourier transform on the image planes;

Step 205, to a single point light source, utilize its coordinate (x _s, y _s), the variable quantity ξ of incident light phase place, scalar aberration matrix W (α ', β ') and Polarization aberration matrix J (α ', β '), when obtaining this spot light, the aerial image I on the desirable image planes _Nom(α _s, β _s) and defocusing amount be the aerial image I on the f image planes _Off(α _s, β _s);

Step 206, judge whether to calculate the corresponding aerial image I of all pointolites _Nom(α _s, β _s) and I _Off(α _s, β _s), if then get into step 207, otherwise return step 205;

Step 207, according to the Abbe method, the aerial image I corresponding to each pointolite _Nom(α _s, β _s) superpose, obtain the aerial image I on the desirable image planes _Nom, the aerial image I corresponding to each pointolite _Off(α _s, β _s) superpose, obtain the aerial image I on the image planes that defocusing amount is f _Off

In the step 205 according to the invention, the aerial image I that the acquisition point light source is corresponding _Nom(α _s, β _s) and I _Off(α _s, β _s) detailed process be:

The setting global coordinate system is: the direction with optical axis is the z axle, and according to the left-handed coordinate system principle with the z axle set up global coordinate system (x, y, z);

Step 301, according to pointolite coordinate (x _s, y _s), the light wave that the calculation level light source sends is through the near field distribution E of N * N sub regions on the mask; Wherein, E is the vector matrix of N * N, and its each element is one 3 * 1 vector, 3 components of the diffraction near field distribution of mask in the expression global coordinate system;

Step 302, according near field distribution E obtain light wave the Electric Field Distribution

at optical projection system entrance pupil rear wherein be the vector matrix of N * N; Its each element is one 3 * 1 vector, 3 components of the Electric Field Distribution at entrance pupil rear in the expression global coordinate system;

Step 303, to establish light wave direction of propagation in optical projection system approximate parallel with optical axis; Further according to Electric Field Distribution

the scalar aberration matrix W at entrance pupil rear (α '; β ') and the Polarization aberration matrix J (α '; β '); Obtain light wave wherein in the Electric Field Distribution

in optical projection system emergent pupil the place ahead; The Electric Field Distribution in emergent pupil the place ahead

is the vector matrix of N * N; Its each element is one 3 * 1 vector, 3 components of the Electric Field Distribution in emergent pupil the place ahead in the expression global coordinate system;

Step 304, according to the projection system in front of the exit pupil of the electric field distribution

Get behind the exit pupil of the projection system of the electric field distribution

Step 305, utilize Wolf Wolf optical imagery theoretical, according to the Electric Field Distribution at emergent pupil rear And the variable quantity ξ of incident light phase place, obtain the Electric Field Distribution on the desirable image planes

With defocusing amount be the Electric Field Distribution on the f image planes And according to

Aerial image I on the desirable image planes of acquisition point light source correspondence _Nom(α _s, β _s), according to The defocusing amount that the acquisition point light source is corresponding is the aerial image I on the f image planes _Off(α _s, β _s).

Beneficial effect

The present invention has considered the influence of scalar aberration, Polarization aberration and the defocusing amount of imperfect etching system in the process of obtaining the etching system aerial image, therefore optimization method of the present invention is applicable to imperfect etching system.

Secondly, the vector imaging model that utilizes among the present invention has been considered the vectorial property of electromagnetic field in obtaining the process of aerial image, makes mask after optimizing not only be applicable to the etching system of little NA, also is applicable to the etching system of NA＞0.6.

Once more, the present invention utilizes the gradient information of optimization aim function, in conjunction with steepest prompt drop method mask pattern is optimized, and optimization efficiency is high.

Description of drawings

Fig. 1 is the process flow diagram of optimization method that the present invention is based on the imperfect etching system OPC of Abbe vector imaging model.

Fig. 2 sends light wave forms aerial image on wafer position after mask, optical projection system synoptic diagram for pointolite.

Fig. 3 departs from the synoptic diagram of desirable image planes for wafer position.

Fig. 4 is for carrying out the synoptic diagram of rasterizing in the embodiment of the invention to partial coherence light source face.

Fig. 5 is the scalar aberration of the optical projection system of specific lithography system and the corrugated synoptic diagram of Polarization aberration (the Jones pupil is represented).

Fig. 6 is under the unpolarized illumination during aberrationless, and the initial mask that intensive lines are corresponding, the mask after optimizing carry out the synoptic diagram of the optimization mask

after the periodicity continuation with the mask core

of square window intercepting and based on

.

Fig. 7 is under the unpolarized illumination during aberrationless, the initial mask that intensive lines are corresponding and through the corresponding process window synoptic diagram of optimization mask

after the continuation periodically.

Fig. 8 is that the mask

after the initial mask that intensive lines are corresponding, the optimization carries out the synoptic diagram of the optimization mask after the periodically continuation when under the unpolarized illumination aberration being arranged with the mask core

of square window intercepting and based on

.

Fig. 9 is when under the unpolarized illumination aberration being arranged, the corresponding process window synoptic diagram of optimization mask

after initial mask that intensive lines are corresponding and the continuation of process periodicity.

Embodiment

Further the present invention is elaborated below in conjunction with accompanying drawing.

Principle of the present invention: the technique change factor in the actual light etching system mainly comprises: four kinds of variation of exposure, out of focus, scalar aberration and Polarization aberration etc.Wherein scalar aberration and Polarization aberration mainly are that phase place to the optical projection system incident light exerts an influence, and after employed etching system was determined, the method for ray tracing capable of using was obtained the scalar aberration and the Polarization aberration of optical projection system.Etching system can be estimated with process window the stability of variation of exposure and out of focus.The transverse axis of process window is the out of focus degree of depth (Depth of focus DOF), is illustrated under the acceptable prerequisite of image quality the maximum disparity between actual wafer position and the desirable image planes.The longitudinal axis of process window is exposure depth (Exposure latitude EL), is illustrated under the acceptable prerequisite of image quality acceptable variation of exposure scope; Usually the variable quantity that EL is expressed as exposure accounts for the form of the number percent of demarcating exposure.The opening of process window has comprised all and has satisfied the corresponding combination of DOF with the EL of particular manufacturing process requirement.Above-mentioned specific manufacture process requirement generally comprises critical size (CD) error, the isoparametric requirement of side wall angle of imaging profile in the photoresist.When the corresponding process window opening of etching system is big, this system stable higher to variation of exposure and out of focus then.

In order on transverse axis (DOF) direction, to enlarge the process window opening, promptly under the acceptable prerequisite of image quality, enlarge the gap between actual wafer position and the desirable image planes.The present invention is configured to objective function D the imaging evaluation function D at desirable image planes place ₁With defocusing amount be the imaging evaluation function D at the image planes place of f ₂Linear combination, i.e. D=η D ₁+ (1-η) D ₂, wherein η ∈ (0,1) is a weighting coefficient.

In order on the longitudinal axis (EL) direction, to enlarge the process window opening, promptly under the acceptable prerequisite of image quality, enlarge acceptable variation of exposure scope.Method of the present invention should make the pairing aerial image of the OPC after the optimization as far as possible near targeted graphical.Its reason is: when aerial image during near targeted graphical, aerial image distributes and has more steep side wall angle, thereby helps forming the side wall angle of imaging profile in the more steep photoresist; Simultaneously, it is less that aerial image is distributed in live width difference corresponding on the xsect of differing heights, can reduce the CD error that is caused by variation of exposure.The size of hypothetical target figure is N * N, the present invention evaluation function D that forms images ₁Be set at aerial image and the Euler's distance between the targeted graphical behind the amplitude modulation(PAM) on the desirable image planes square, promptly

Wherein

Be the pixel value of targeted graphical, I _Nom(x is the pixel value of the aerial image on the corresponding desirable image planes of current mask y), and ω ∈ (0,1) is an amplitude modulation coefficient.Imaging evaluation function D ₂Be set at defocusing amount and be aerial image and the Euler's distance between the targeted graphical behind the amplitude modulation(PAM) on the f image planes square, promptly

I wherein _Off(x is the pixel value of the aerial image on the f image planes for the corresponding defocusing amount of current mask y).

As shown in Figure 1, the present invention is based on the optimization method of the imperfect etching system OPC of Abbe vector imaging model, concrete steps are:

Step 101, mask pattern M is initialized as size is the targeted graphical of N * N

.

Step 102, the transmissivity that initial mask pattern M upper shed part is set are 1, and the transmissivity in resistance light zone is 0; Set the matrix of variables Ω of N * N: as M (x; O'clock y)=1;

is as M (x; O'clock y)=0;

be M (x, y) transmissivity of each pixel on the expression mask pattern wherein.

Step 103, objective function D is configured to the imaging evaluation function D at desirable image planes place ₁With defocusing amount be the imaging evaluation function D at f image planes place ₂Linear combination, i.e. D=η D ₁+ (1-η) D ₂, wherein η ∈ (0,1) is a weighting coefficient.

Imaging evaluation function D ₁Be set at aerial image and the Euler's distance between the targeted graphical behind the amplitude modulation(PAM) on the desirable image planes square, promptly

Wherein

Be the pixel value of targeted graphical, I _Nom(x is the pixel value of the aerial image on the corresponding desirable image planes of current mask y), and ω ∈ (0,1) is an amplitude modulation coefficient.

Imaging evaluation function D ₂Be set at defocusing amount and be aerial image and the Euler's distance between the targeted graphical behind the amplitude modulation(PAM) on the f image planes square, promptly

I wherein _Off(x is the pixel value of the aerial image on the f image planes for the corresponding defocusing amount of current mask y).

In the step 103 according to the invention, aerial image on the desirable image planes of current mask correspondence and the corresponding defocusing amount of current mask are that the acquisition process of the aerial image on the f image planes is:

Variable predefine

As shown in Figure 2, the direction of setting optical axis is the z axle, and according to the left-handed coordinate system principle with the z axle set up global coordinate system (x, y, z).If the world coordinates of any point light source is (x on the partial coherence light source face _s, y _s, z _s), the direction cosine of being sent and be incident to the plane wave of mask by this pointolite are (α _s, β _s, γ _s), then the relation between world coordinates and the direction cosine is:

α _s＝x _s·NA _m，β _s＝y _s·NA _m， ${\mathrm{\γ}}_s=\cos \left[{\sin }^{-1}({\mathrm{NA}}_m\·\sqrt{x_s^2+y_s^2})\right]$

Wherein, NA _mBe optical projection system object space numerical aperture.

If the world coordinates of any point is on the mask (x, y, z), based on diffraction principle; The direction cosine that are incident to the plane wave of optical projection system entrance pupil from mask are (α, beta, gamma), wherein (α; Beta, gamma) be that mask (object plane) is gone up global coordinate system (x, y z) are carried out coordinate system behind the Fourier transform.

If it is (x that wafer (image planes) is gone up the world coordinates of any point _w, y _w, z _w), the direction cosine that are incident to the plane wave of image planes from the optical projection system emergent pupil are (α ', β ', γ '), and wherein (α ', β ', γ ') be that wafer (image planes) is gone up global coordinate system (x _w, y _w, z _w) carry out the coordinate system behind the Fourier transform.

Transformational relation between global coordinate system and the local coordinate system:

Set up local coordinate system (e _⊥, e _P), e _⊥The direction of vibration of axle middle TE polarized light for light source emits beam, e _PThe direction of vibration of axle middle TM polarized light for light source emits beam.The plane that wave vector is made up of wave vector and optical axis for

is called the plane of incidence; The direction of vibration of TM polarized light is in the plane of incidence, and the direction of vibration of TE polarized light is perpendicular to the plane of incidence.Then the transformational relation of global coordinate system and local coordinate system is:

$\left[\begin{array}{c}{E}_x\\ E_y\\ E_z\end{array}\right]=T\·\left[\begin{array}{c}{E}_{\⊥}\\ E_P\end{array}\right]$

Wherein, E _x, E _yAnd E _zBe respectively that light source sends the component of light wave electric field in global coordinate system, E _⊥And E _PBe that light source sends the component of light wave electric field in local coordinate system, transition matrix T is:

$T=\left[\begin{array}{cc}-\frac{\mathrm{\β}}{\mathrm{\ρ}}& -\frac{\mathrm{\α\γ}}{\mathrm{\ρ}}\\ \frac{\mathrm{\α}}{\mathrm{\ρ}}& -\frac{\mathrm{\β\γ}}{\mathrm{\ρ}}\\ 0& \mathrm{\ρ}\end{array}\right]$

Wherein, $\mathrm{\ρ}=\sqrt{{\mathrm{\α}}^2+{\mathrm{\β}}^2}.$

In the actual light etching system, there is the phenomenon that departs from desirable image planes in the position of wafer, and the distance between the two is represented with δ.As shown in Figure 3.301 is the distance of the physical location of wafer to desirable image planes, and its influence to imaging is embodied in the variation of light path, shown in 302, can be got by geometric relationship among the figure:

Optical_pach＝n _wδ(1-cosθ)

Wherein, n _wBe the refractive index of etching system picture side immersion liquid, θ is the angle of light and optical axis.

The acquisition process of aerial image is following:

Step 201, mask pattern M grid is turned to N * N sub regions.

Step 202, surface of light source is tiled into a plurality of zones, each zone is approximate with pointolite, each grid region center point coordinate (x _s, y _s) represent the pairing pointolite coordinate of this grid region.As shown in Figure 4, method among the present invention is with the equidistant straight line that is parallel to X axle and Y direction, and the surface of light source grid of partial coherence light source is turned to the equal little square of size.

Step 203, according to required obtain residing image planes of aerial image and desirable image planes apart from δ, obtain the variable quantity ξ of the etching system incident light phase place that causes by said δ; Wherein to the aerial image on the desirable image planes, then δ=0 is the aerial image on the f image planes, then δ=f to defocusing amount.

Because the physical location of wafer can change because of the influence of factors such as control in the etching system, thereby cause the position of the desirable image planes of actual image planes position deviation etching system, produce defocusing amount; Above-mentioned defocusing amount can be brought the variation of etching system incident light phase place, and variable quantity ξ does

$\mathrm{\ξ}=k^{\′}\·n_w\·\mathrm{\δ}\·(1-{\mathrm{\γ}}^{\′})=k^{\′}\·n_w\·\mathrm{\δ}\·(1-\sqrt{1-{\mathrm{\α}}^{\′2}-{\mathrm{\β}}^{\′2}}),$

Wherein $k^{\′}=\frac{2\mathrm{\π}{n}_w}{\mathrm{\λ}}$ Be wave number.

When finding the solution the aerial image on the desirable image planes, δ=0, finding the solution defocusing amount is the aerial image on the f image planes, δ=f.

Step 204, the scalar aberration matrix W (α ', β ') of obtaining optical projection system and Polarization aberration matrix J (α ', β '), wherein (α ', β ', γ ') is that global coordinate system carries out the coordinate system behind the Fourier transform on the image planes.

Because it is nonideal optical system that factors such as processing, debug causes optical projection system, it can produce certain influence to the phase place of incident light equally.To the optical projection system of low numerical aperture, suppose to have identical amplitude before the light wave in the whole pupil scope of optical projection system, this moment, only need were described the imperfection of optical projection system with scalar aberration matrix W (α ', β ').But along with the increase of optical projection system numerical aperture, the vector imaging characteristic of light wave is more remarkable to the aerial image on wafer position influence, so the present invention further considers the influence of Polarization aberration J (α ', β ') to the aerial image on the wafer position.

Scalar aberration matrix W (α ', β ') and Polarization aberration matrix J (α ', β ') are the matrix of N * N; Each element is a numerical value in W (α ', the β ') matrix, the actual corrugated at its expression emergent pupil place and the wavelength number that desirable corrugated differs; J (α ', β ') be the vector matrix of one N * N, each matrix element is a Jones matrix, because TE and TM polarized light through transition matrix, all be expressed as the form of xy component, so Jones matrix concrete form are:

$J({\mathrm{\α}}^{\′},{\mathrm{\β}}^{\′},m,n)=\left(\begin{array}{cc}{J}_{\mathrm{xy}}({\mathrm{\α}}^{\′},{\mathrm{\β}}^{\′},m,n)& J_{\mathrm{xy}}({\mathrm{\α}}^{\′},{\mathrm{\β}}^{\′},m,n)\\ J_{\mathrm{yx}}({\mathrm{\α}}^{\′},{\mathrm{\β}}^{\′},m,n)& J_{\mathrm{yy}}({\mathrm{\α}}^{\′},{\mathrm{\β}}^{\′},m,n)\end{array}\right)$ m，n＝1，2，...，N

J _{I ', j}' (α ', β ', m, n) (i '=x, y; J '=x, y) expression incident i ' polarized light is through becoming the ratio of j ' polarized light after the optical projection system.

Step 205, to a single point light source, utilize its coordinate (x _s, y _s), the variable quantity ξ of incident light phase place, scalar aberration matrix W (α ', β ') and Polarization aberration matrix J (α ', β '), when obtaining this spot light, the aerial image I on the desirable image planes _Nom(α _s, β _s) and defocusing amount be the aerial image I on the f image planes _Off(α _s, β _s).

Step 206, judge whether to calculate the corresponding aerial image I of all pointolites _Nom(α _s, β _s) and I _Off(α _s, β _s), if then get into step 207, otherwise return step 205.

Step 207, according to the Abbe method, the aerial image I corresponding to each pointolite _Nom(α _s, β _s) superpose, obtain the aerial image I on the desirable image planes _Nom, the aerial image I corresponding to each pointolite _Off(α _s, β _s) superpose, obtain the aerial image I on the image planes that defocusing amount is f _Off

In the step 205 according to the invention, obtain aerial image I _Nom(α _s, β _s) and I _Off(α _s, β _s) detailed process be:

Step 301, according to pointolite coordinate (x _s, y _s), the light wave that the calculation level light source sends is through the near field distribution E of N * N sub regions on the mask.

Wherein, E is that the vector matrix of N * N is (if all elements of a matrix is matrix or vector; Then be called vector matrix), each element in this vector matrix is one 3 * 1 vector, 3 components of the diffraction near field distribution of mask in the expression global coordinate system.E representes that two matrix corresponding elements multiply each other.

is the vector matrix of one N * N, and each element is the electric field intensity of electric field in global coordinate system that pointolite sends light wave; As establish the electric field that a pointolite on the partial coherence light source sends light wave and in local coordinate system, be expressed as

Then this electric field is expressed as in global coordinate system:

${{\stackrel{u}{E}}_i}^{\′}=T\·{\stackrel{u}{E}}_i$

The diffraction matrices B of mask is the scalar matrix of one N * N, and each element is scalar in the scalar matrix, and approximate according to Hopkins (Thelma Hopkins), each element of B can be expressed as:

$B(m,n)=\exp \left(\frac{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000090475100000042.png,HDA0000090475100000052.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{\mathrm{\&beta;}}_{s}x}{\mathrm{\&lambda;}}\right)\exp \left(\frac{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000090475100000042.png,HDA0000090475100000052.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{\mathrm{\&alpha;}}_{s}y}{\mathrm{\&lambda;}}\right)$

$=\mathrm{Exp}\left(\frac{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000090475100000042.png,HDA0000090475100000052.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{\mathrm{\&beta;}}_{s}m\&times;\mathrm{Pixel}}{\mathrm{\&lambda;}}\right)\mathrm{Exp}\left(\frac{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000090475100000042.png,HDA0000090475100000052.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{\mathrm{\&alpha;}}_{s}n\&times;\mathrm{Pixel}}{\mathrm{\&lambda;}}\right),$ M, n=1,2 ..., N wherein, pixel representes the length of side of all subregion on the mask pattern.

Step 302, obtain the Electric Field Distribution of light wave at optical projection system entrance pupil rear according near field distribution E

$E_b^{\mathrm{ent}}(\mathrm{\&alpha;},\mathrm{\&beta;}).$

The detailed process of this step is:

Because each subregion on the mask can be regarded a secondary sub-light source as, the center of the subregion coordinate as this subregion is theoretical according to Fourier optics, can the Electric Field Distribution in optical projection system entrance pupil the place ahead be expressed as the function of α and β:

$E_l^{\mathrm{ent}}(\mathrm{\&alpha;},\mathrm{\&beta;})=\frac{\mathrm{\&gamma;}}{\mathrm{j\&lambda;}}\frac{e^{-\mathrm{jkr}}}{r}F\left\{E\right\}---\left(3\right)$

Wherein, Owing to have N * N sub regions on the mask; Therefore the Electric Field Distribution

in entrance pupil the place ahead is the vector matrix of N * N; Each element in this vector matrix is one 3 * 1 vector, 3 components of the Electric Field Distribution in entrance pupil the place ahead in the expression global coordinate system.F{} representes Fourier transform, and r is the entrance pupil radius,

Be wave number, λ is the wavelength that pointolite sends light wave, n _mBe the object space medium refraction index.

Because the reduction magnification of optical projection system is bigger; Be generally 4 times; This moment, the numerical aperture of object space was less; Cause the axial component of entrance pupil the place ahead Electric Field Distribution

to ignore, so optical projection system entrance pupil the place ahead is identical with the Electric Field Distribution at entrance pupil rear, promptly

$E_b^{\mathrm{ent}}(\mathrm{\&alpha;},\mathrm{\&beta;})=E_l^{\mathrm{ent}}(\mathrm{\&alpha;},\mathrm{\&beta;})=\frac{\mathrm{\&gamma;}}{\mathrm{j\&lambda;}}\frac{e^{-\mathrm{jkr}}}{r}F\left\{E\right\}---\left(4\right)$

Wherein, Owing to have N * N sub regions on the mask; Therefore the Electric Field Distribution

at entrance pupil rear is the vector matrix of N * N; Each element in this matrix is one 3 * 1 vector, 3 components of the Electric Field Distribution at entrance pupil rear in the expression global coordinate system.

Step 303, to establish light wave direction of propagation in optical projection system approximate parallel with optical axis; Further according to Electric Field Distribution

the scalar aberration matrix W at entrance pupil rear (α '; β ') and the Polarization aberration matrix J (α '; β '), obtain the Electric Field Distribution

of light wave in optical projection system emergent pupil the place ahead

The detailed process of this step is:

For aberrationless preferred view system, the mapping process of entrance pupil rear and emergent pupil the place ahead Electric Field Distribution can be expressed as the form of a low-pass filter function and a modifying factor product, that is:

${\hat{E}}_l^{\mathrm{ext}}({\mathrm{\&alpha;}}^{\&prime;},{\mathrm{\&beta;}}^{\&prime;})=\mathrm{cUe}{E}_b^{\mathrm{ent}}(\mathrm{\&alpha;},\mathrm{\&beta;})$

Wherein, The Electric Field Distribution in emergent pupil the place ahead is the vector matrix of N * N; Each element in this vector matrix is one 3 * 1 vector, 3 components of the Electric Field Distribution in emergent pupil the place ahead in the expression global coordinate system; C is the constant correction factor, and low-pass filter function U is the scalar matrix of N * N, and the numerical aperture of expression optical projection system is 1 in the inner value of pupil promptly to the limited receiving ability of diffraction spectrum, and the outside value of pupil is 0, the concrete expression as follows:

$U=\left\{\begin{array}{cc}1& \sqrt{{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="HDA0000090475100000042.png,HDA0000090475100000052.png"\; state="\{\{state\}\}">f</figure-callout>}}^2+{\mathrm{<figure-callout\; id="2"\; label="g"\; filenames="HDA0000090475100000042.png,HDA0000090475100000052.png"\; state="\{\{state\}\}">g</figure-callout>}}^2}\&le;1\\ 0& \mathrm{elsewhere}\end{array}\right.$

Wherein, (f g) is normalized world coordinates on the entrance pupil.

Constant correction factor c can be expressed as:

$c=\frac{r}{r^{\&prime;}}\sqrt{\frac{{\mathrm{\&gamma;}}^{\&prime;}}{\mathrm{\&gamma;}}}\frac{n_w}{R}$

Wherein, r and r ' are respectively optical projection system entrance pupil and emergent pupil radius, n _wBe the refractive index of etching system picture side immersion liquid, R is the reduction magnification of preferred view system, is generally 4.

Because the approximate optical axis that is parallel in the direction of propagation of light wave between optical projection system entrance pupil and emergent pupil, therefore for arbitrarily (α ', β '), the entrance pupil rear is identical with phase differential between emergent pupil the place ahead.Owing to finally will find the solution the aerial image (being light distribution) on the wafer, so the constant phase difference in entrance pupil rear and emergent pupil the place ahead can be ignored.Thereby the Electric Field Distribution that can obtain emergent pupil the place ahead is:

${\hat{E}}_l^{\mathrm{ext}}({\mathrm{\&alpha;}}^{\&prime;},{\mathrm{\&beta;}}^{\&prime;})=\frac{1}{{\mathrm{\&lambda;r}}^{\&prime;}}\sqrt{{\mathrm{\&gamma;}}^{\&prime;}\mathrm{\&gamma;}}\frac{n_w}{R}\mathrm{UeF}\left\{E\right\}$

Because it is nonideal optical system that factors such as processing, debug causes optical projection system; Therefore according to the Electric Field Distribution in desired light etching system emergent pupil the place ahead; Consider the influence of scalar aberration W (α ', β ') and the Polarization aberration J (α ', β ') of imperfect etching system; Obtain the Electric Field Distribution in imperfect etching system emergent pupil the place ahead

$E_l^{\mathrm{ext}}({\mathrm{\&alpha;}}^{\&prime;},{\mathrm{\&beta;}}^{\&prime;})=\frac{1}{{\mathrm{\&lambda;r}}^{\&prime;}}\sqrt{{\mathrm{\&gamma;}}^{\&prime;}\mathrm{\&gamma;}}\frac{n_w}{R}\mathrm{UeJ}({\mathrm{\&alpha;}}^{\&prime;},{\mathrm{\&beta;}}^{\&prime;})\mathrm{eF}\left\{E\right\}{\mathrm{<figure-callout\; id="2"\; label="ee\; j"\; filenames="HDA0000090475100000042.png,HDA0000090475100000052.png"\; state="\{\{state\}\}">ee</figure-callout>}}^j---\left(5\right)$

Step 304, according to the projection system in front of the exit pupil of the electric field distribution

Get behind the exit pupil of the projection system of the electric field distribution

The rotation effect of TM component between emergent pupil the place ahead and rear according to electromagnetic field; If in the global coordinate system, the forward and backward side's of emergent pupil electric field is expressed as: each element of the vector matrix of N * N

and

and

is following:

$E_l^{\mathrm{ext}}({\mathrm{\&alpha;}}^{\&prime;},{\mathrm{\&beta;}}^{\&prime;},m,n)={[E_{\mathrm{lx}}^{\mathrm{ext}}({\mathrm{\&alpha;}}^{\&prime;},{\mathrm{\&beta;}}^{\&prime;},m,n);E_{\mathrm{ly}}^{\mathrm{ext}}({\mathrm{\&alpha;}}^{\&prime;},{\mathrm{\&beta;}}^{\&prime;},m,n);E_{\mathrm{lz}}^{\mathrm{ext}}({\mathrm{\&alpha;}}^{\&prime;},{\mathrm{\&beta;}}^{\&prime;},m,n)]}^T$

$E_b^{\mathrm{ext}}({\mathrm{\&alpha;}}^{\&prime;},{\mathrm{\&beta;}}^{\&prime;},m,n)={[E_{\mathrm{bx}}^{\mathrm{ext}}({\mathrm{\&alpha;}}^{\&prime;},{\mathrm{\&beta;}}^{\&prime;},m,n);E_{\mathrm{by}}^{\mathrm{ext}}({\mathrm{\&alpha;}}^{\&prime;},{\mathrm{\&beta;}}^{\&prime;},m,n);E_b^{\mathrm{ext}}({\mathrm{\&alpha;}}^{\&prime;},{\mathrm{\&beta;}}^{\&prime;},m,n)]}^T$

Wherein, M; N=1; 2; ...; N; α '=cos φ ' sin θ ', β '=sin φ ' sin θ ', γ '=cos θ '; Be that the direction cosine (wave vector) that the optical projection system emergent pupil is incident to the plane wave of image planes are that φ ' and θ ' are respectively the position angle and the elevation angle of wave vector, then the relational expression of

and

is:

$E_b^{\mathrm{ext}}({\mathrm{\&alpha;}}^{\&prime;},{\mathrm{\&beta;}}^{\&prime;})=\mathrm{Ve}{E}_l^{\mathrm{ext}}({\mathrm{\&alpha;}}^{\&prime;},{\mathrm{\&beta;}}^{\&prime;})---\left(6\right)$

Wherein, V is the vector matrix of a N * N, and each element is one 3 * 3 matrix:

$V(m,n)=\left[\begin{array}{ccc}{\cos \mathrm{\&phi;}}^{\&prime;}& {-\sin \mathrm{\&phi;}}^{\&prime;}& 0\\ {\sin \mathrm{\&phi;}}^{\&prime;}& {\cos \mathrm{\&phi;}}^{\&prime;}& 0\\ 0& 0& 1\end{array}\right]\&CenterDot;\left[\begin{array}{ccc}{\cos \mathrm{\&theta;}}^{\&prime;}& 0& {\sin \mathrm{\&theta;}}^{\&prime;}\\ 0& 0& 1\\ {-\sin \mathrm{\&theta;}}^{\&prime;}& 0& {\cos \mathrm{\&theta;}}^{\&prime;}\end{array}\right]\&CenterDot;\left[\begin{array}{ccc}{\cos \mathrm{\&phi;}}^{\&prime;}& {\sin \mathrm{\&phi;}}^{\&prime;}& 0\\ {-\sin \mathrm{\&phi;}}^{\&prime;}& {\cos \mathrm{\&phi;}}^{\&prime;}& 0\\ 0& 0& 1\end{array}\right]$

$=\left[\begin{array}{ccc}{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HDA0000090475100000042.png,HDA0000090475100000052.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2{\mathrm{\&phi;}}^{\&prime;}{\cos \mathrm{\&theta;}}^{\&prime;}+{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HDA0000090475100000042.png,HDA0000090475100000052.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2{\mathrm{\&phi;}}^{\&prime;}& \cos {\mathrm{\&phi;}}^{\&prime;}\sin {\mathrm{\&phi;}}^{\&prime;}(\cos {\mathrm{\&theta;}}^{\&prime;}-1)& \cos {\mathrm{\&phi;}}^{\&prime;}\sin {\mathrm{\&theta;}}^{\&prime;}\\ \cos {\mathrm{\&phi;}}^{\&prime;}\sin {\mathrm{\&phi;}}^{\&prime;}({\cos \mathrm{\&theta;}}^{\&prime;}-1)& {\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HDA0000090475100000042.png,HDA0000090475100000052.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2{\mathrm{\&phi;}}^{\&prime;}\cos {\mathrm{\&theta;}}^{\&prime;}+{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HDA0000090475100000042.png,HDA0000090475100000052.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2{\mathrm{\&phi;}}^{\&prime;}& \sin {\mathrm{\&phi;}}^{\&prime;}\sin {\mathrm{\&theta;}}^{\&prime;}\\ {-\cos \mathrm{\&phi;}}^{\&prime;}{\sin \mathrm{\&theta;}}^{\&prime;}& -{\sin \mathrm{\&phi;}}^{\&prime;}\sin {\mathrm{\&theta;}}^{\&prime;}& \cos {\mathrm{\&theta;}}^{\&prime;}\end{array}\right]$

$=\left[\begin{array}{ccc}\frac{{\mathrm{\&beta;}}^{\&prime;2}+{\mathrm{\&alpha;}}^{\&prime;2}{\mathrm{\&gamma;}}^{\&prime;}}{1-{\mathrm{\&gamma;}}^{\&prime;2}}& -\frac{{\mathrm{\&alpha;}}^{\&prime;}{\mathrm{\&beta;}}^{\&prime;}}{1+{\mathrm{\&gamma;}}^{\&prime;}}& {\mathrm{\&alpha;}}^{\&prime;}\\ -\frac{{\mathrm{\&alpha;}}^{\&prime;}{\mathrm{\&beta;}}^{\&prime;}}{1+{\mathrm{\&gamma;}}^{\&prime;}}& \frac{{\mathrm{\&alpha;}}^{\&prime;2}+{\mathrm{\&beta;}}^{\&prime;2}{\mathrm{\&gamma;}}^{\&prime;}}{1-{\mathrm{\&gamma;}}^{\&prime;2}}& {\mathrm{\&beta;}}^{\&prime;}\\ {-\mathrm{\&alpha;}}^{\&prime;}& {-\mathrm{\&beta;}}^{\&prime;}& {\mathrm{\&gamma;}}_{\&prime;}\end{array}\right]$ m，n＝1，2，...，N

Step 305, utilize Wolf Wolf optical imagery theoretical, according to the Electric Field Distribution at emergent pupil rear Obtain the Electric Field Distribution on the desirable image planes

And according to Aerial image I on the acquisition point light source corresponding ideal image planes _Nom(α _s, β _s).

Utilize Wolf Wolf optical imagery theoretical, according to the Electric Field Distribution at emergent pupil rear

And the variable quantity ξ of incident light phase place, obtaining defocusing amount is the Electric Field Distribution on the f image planes

And according to

The corresponding defocusing amount of acquisition point light source is the aerial image I on the f image planes _Off(α _s, β _s).

The detailed process of this step is:

When not considering the variable quantity ξ of the caused etching system incident light of imperfect etching system defocusing amount δ phase place, the Electric Field Distribution on the wafer position is shown in (7) formula:

${\hat{E}}^{\mathrm{wafer}}=\frac{2\mathrm{\&pi;\&lambda;}{r}^{\&prime;}}{{\mathrm{jn}}_w^2}{e}^{j{k}^{\&prime;}{r}^{\&prime;}{F}^{-1}}\left\{\frac{1}{{\mathrm{\&gamma;}}^{\&prime;}}{E}_b^{\mathrm{ext}}\right\}---\left(7\right)$

Wherein, F-1{} is an inverse Fourier transform.In (5) and (6) formula substitutions (7) formula, and ignore the constant phase item, can get:

${\hat{E}}^{\mathrm{wafer}}=\frac{2\mathrm{\&pi;}}{n_{w}R}{F}^{-1}\left\{\sqrt{\frac{\mathrm{\&gamma;}}{{\mathrm{\&gamma;}}^{\&prime;}}}\mathrm{eVeUe\; J}({\mathrm{\&alpha;}}^{\&prime;},{\mathrm{\&beta;}}^{\&prime;})\mathrm{eF}\right\{E\left\}e{e}^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000090475100000042.png,HDA0000090475100000052.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;W}({\mathrm{\&alpha;}}^{\&prime;},{\mathrm{\&beta;}}^{\&prime;})}\right\}---\left(8\right)$

Be directed to imperfect etching system, when the image planes of computer memory picture and desirable image planes exist apart from δ, then need consider the influence that the variation ξ of the caused etching system incident light of δ phase place is brought.

Electric Field Distribution on the then imperfect etching system is:

$E^{\mathrm{wafer}}=\frac{2\mathrm{\&pi;\&lambda;}{r}^{\&prime;}}{{\mathrm{jn}}_w^2}{e}^{j{k}^{\&prime;}{r}^{\&prime;}}{F}^{-1}\left\{\frac{e^{\mathrm{j\&xi;}}}{{\mathrm{\&gamma;}}^{\&prime;}}e{E}_b^{\mathrm{ext}}\right\}---\left(9\right)$

Make δ=f, then

is the Electric Field Distribution on the f image planes for defocusing amount.

Make δ=0, then is the Electric Field Distribution on the desirable image planes.

(1) formula, (5) formula and (6) formula are updated in (9) formula, can obtain pointolite (α _s, β _s) light distribution of image planes when throwing light on, that is:

$E^{\mathrm{wafer}}({\mathrm{\&alpha;}}_s,{\mathrm{\&beta;}}_s)=\frac{2\mathrm{\&pi;}}{n_{w}R}{F}^{-1}\left\{\sqrt{\frac{\mathrm{\&gamma;}}{{\mathrm{\&gamma;}}^{\&prime;}}}e{e}^{\mathrm{j\&xi;}}\mathrm{eVeUeJ}\left({\mathrm{\&alpha;}}^{\&prime;}{\mathrm{\&beta;}}^{\&prime;}\right)\mathrm{eF}\right\{E_{i}e_{\&prime;}\mathrm{BeM}\left\}e{e}^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000090475100000042.png,HDA0000090475100000052.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;W}({\mathrm{\&alpha;}}^{\&prime;},{\mathrm{\&beta;}}^{\&prime;})}\right\}---\left(10\right)$

Because E _i' middle element value and mask coordinate are irrelevant, so following formula can be write as:

$E^{\mathrm{wafer}}({\mathrm{\&alpha;}}_s,{\mathrm{\&beta;}}_s)=\frac{2\mathrm{\&pi;}}{{\mathrm{nw}}_R}{F}^{-1}\left\{V^{\&prime;}\right\}\&CircleTimes;\left(\mathrm{BeM}\right)$

Wherein

The expression convolution, $V^{\&prime;}=\sqrt{\frac{\mathrm{\&gamma;}}{{\mathrm{\&gamma;}}^{\&prime;}}}e{e}^{\mathrm{J\&xi;}({\mathrm{\&alpha;}}^{\&prime;},{\mathrm{\&beta;}}^{\&prime;})}\mathrm{EVeUeJ}({\mathrm{\&alpha;}}^{\&prime;},{\mathrm{\&beta;}}^{\&prime;})e{E}_{i}e_{\&prime;}{\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="HDA0000090475100000042.png,HDA0000090475100000052.png"\; state="\{\{state\}\}">e</figure-callout>}}^j$ Be the vector matrix of N * N, each matrix element is 3 * 1 vector (v _x', v _y', v _z') ^T, v wherein _x', v _y', v _z' be the function of α ' and β '.

E then ^Wafer(α _s, β _s) three components in global coordinate system do

$E_P^{\mathrm{wafer}}({\mathrm{\&alpha;}}_s,{\mathrm{\&beta;}}_s)=H_p\&CircleTimes;\left(\mathrm{BeM}\right)$

Wherein,

p=x; Y; Z, wherein Vp ' is the scalar matrix of N * N, is made up of the x component of each element of vector matrix V '.

$I({\mathrm{\&alpha;}}_s,{\mathrm{\&beta;}}_s)=\underset{p=x,y,x}{\mathrm{\&Sigma;}}{\left|\right|H_p\&CircleTimes;\left(\mathrm{BeM}\right)\left|\right|}_2^2$

Wherein

expression is to the matrix delivery and ask square.H wherein _pBe (α with B _s, β _s) function, be designated as respectively

With

Therefore following formula can be designated as:

$I({\text{\&alpha;}}_s,{\mathrm{\&beta;}}_s)=\underset{p=x,y,x}{\mathrm{\&Sigma;}}{\left|\right|H_p^{{\mathrm{\&alpha;}}_s{\mathrm{\&beta;}}_s}\&CircleTimes;\left(B^{{\mathrm{\&alpha;}}_s{\mathrm{\&beta;}}_s}\mathrm{eM}\right)\left|\right|}_2^2$

Order

In coefficient δ=f, I then _Off(α _s, β _s)=I (α _s, β _s); Order

In coefficient δ=0, I then _Nom(α _s, β _s)=I (α _s, β _s).

Following formula obtains the aerial image I on the corresponding desirable image planes of pointolite _Nom(α _s, β _s) and the corresponding defocusing amount of pointolite be the aerial image I on the f image planes _Off(α _s, β _s); According to the Abbe principle, the aerial image I on the desirable image planes under the partial coherence light illumination in the step 207 then _NomWith defocusing amount be the aerial image I on the image planes of f _OffCan be expressed as:

Order

In coefficient δ=0, then $I_{\mathrm{Nom}}=I=\frac{1}{N_s}\underset{{\mathrm{\&alpha;}}_s}{\mathrm{\&Sigma;}}\underset{{\mathrm{\&beta;}}_s}{\mathrm{\&Sigma;}}\underset{p=x,y,z}{\mathrm{\&Sigma;}}{\left|\right|H_p^{{\mathrm{\&alpha;}}_s{\mathrm{\&beta;}}_s}\&CircleTimes;\left(B^{{\mathrm{\&alpha;}}_s{\mathrm{\&beta;}}_s}\mathrm{EM}\right)\left|\right|}_2^2$

Order

In coefficient δ=f, then $I_{\mathrm{Off}}=I=\frac{1}{N_s}\underset{{\mathrm{\&alpha;}}_s}{\mathrm{\&Sigma;}}\underset{{\mathrm{\&beta;}}_s}{\mathrm{\&Sigma;}}\underset{p=x,y,z}{\mathrm{\&Sigma;}}{\left|\right|H_p^{{\mathrm{\&alpha;}}_s{\mathrm{\&beta;}}_s}\&CircleTimes;\left(B^{{\mathrm{\&alpha;}}_s{\mathrm{\&beta;}}_s}\mathrm{EM}\right)\left|\right|}_2^2$

Wherein, N _sIt is the sampling number of partial coherence light source.If adopt the TE polarization illumination, then (2) formula is set at:

Aerial image on the resulting wafer position is I=I _TEIf adopt the TM polarization illumination, then (2) formula is set at:

Aerial image on the resulting wafer position is I=I _TMIf adopt unpolarized illumination, then the aerial image on the wafer position is

Step 104, calculating target function D are for the gradient matrix

of matrix of variables Ω;

Among the present invention, objective function D can be calculated as for the gradient matrix

of matrix of variables Ω:

$\&dtri;D={\&dtri;D}_1+{\&dtri;D}_2---\left(11\right)$

Wherein,

(12)

Wherein, ^*Conjugate operation is got in expression; ^οExpression is with matrix equal Rotate 180 degree on horizontal and vertical.

can be obtained by (2) type is set to:

derivation obtained. can be obtained by (2) type is set to:

derivation obtained.When adopting the TE polarization illumination, ρ _TE=2, ρ _TM=0; When adopting the TM polarization illumination, ρ _TE=0, ρ _TM=2; When adopting unpolarized illumination, ρ _TE=1, ρ _TM=1.When (12) formula of employing is calculated

; Must the δ in (9) formula be made as 0, thereby calculate gradient corresponding to the imaging evaluation function of desirable image planes.(11) form of the computing formula of

in the formula is identical with (12) formula; But must the δ in (9) formula be made as f, be the gradient of imaging evaluation function at the image planes place of f thereby calculate corresponding to defocusing amount.

Step 105, utilize steepest prompt drop method to upgrade matrix of variables to be Ω ', promptly

s is predefined optimization step-length.The mask pattern

that further obtains corresponding current Ω ' is in the OPC optimizing process; The span of

is

Ω (x; Y) span is Ω (x; Y) ∈ [∞ ,+∞].

Step 106, calculate the corresponding target function value D of current mask pattern

; When D reaches predetermined upper limit value less than predetermined threshold or the number of times that upgrades matrix of variables Ω, get into step 107, matrix of variables Ω is that Ω ' returns step 104 otherwise make.

Step 107, stop to optimize, and be targeted graphical horizontal direction cycle and the smaller of vertical direction in the cycle with the length of side of the said square window of core

of the current mask pattern of square window intercepting

.

Step 108, to

in the horizontal direction with the enterprising line period property continuation of vertical direction; Mask size after continuation is decided to be the figure

that obtains this moment through the mask pattern after optimizing more than or equal to the targeted graphical size.

Embodiment of the present invention:

As shown in Figure 5, (because in the numerical evaluation field, the figure of a two dimension is exactly a matrix in essence to utilize the optical projection system aberration that some place in visual field obtains through ray tracing outside certain of lab design in the emulation.Here in fact be exactly the corresponding two-dimentional skiodrome of scalar aberration matrix that draws, the plain value of the value of each coordinate points and entry of a matrix is one to one on the figure).501 are this visual field point scalar aberration synoptic diagram, 502～509 8 Jones's pupil components for the Polarization aberration of this visual field point.502,503 be respectively J _XxReal part and imaginary part.504,505 be respectively J _XyReal part and imaginary part.506,507 be respectively J _YxReal part and imaginary part.508,509 be respectively J _YyReal part and imaginary part.

As shown in Figure 6; Under the unpolarized illumination during aberrationless, the initial mask that intensive lines are corresponding, the mask

after optimizing carry out the synoptic diagram of the optimization mask

after the periodicity continuation with the mask core

of square window intercepting and based on

.601 is initial two-value mask synoptic diagram, and its critical size is 90nm, and it is 1 that white is represented transmission region, its rate of penetrating, grey representative resistance light zone, and its rate of penetrating is 0.Mask graph is positioned at the XY plane, and lines are parallel with the Y axle.602 of the present invention, a method using optimized mask pattern 603 indicates a mask with a square window to capture the central part

604 based after periodic extension optimizing mask

Fig. 7 is under the unpolarized illumination during aberrationless, the initial mask that intensive lines are corresponding and through the corresponding process window synoptic diagram of optimization mask

after the continuation periodically.701 is the corresponding process window of initial mask, and 702 are the process window through optimization mask

correspondence after the periodicity continuation.

As shown in Figure 8; When under the unpolarized illumination aberration being arranged, the mask

after the initial mask that intensive lines are corresponding, the optimization carries out the synoptic diagram of the optimization mask

after the periodically continuation with the mask core

of square window intercepting and based on

.801 is initial two-value mask synoptic diagram, and its critical size is 90nm, and it is 1 that white is represented transmission region, its rate of penetrating, grey representative resistance light zone, and its rate of penetrating is 0.Mask graph is positioned at the XY plane, and lines are parallel with the Y axle.802 of the present invention, a method using optimized mask pattern

803 indicates a mask with a square window to capture the central part

804 based

after periodic extension optimizing mask

Fig. 9 is when under the unpolarized illumination aberration being arranged, the corresponding process window synoptic diagram of optimization mask

after initial mask that intensive lines are corresponding and the continuation of process periodicity.901 is the corresponding process window of initial mask, and 902 are the process window through optimization mask correspondence after the periodicity continuation.

Contrast 701,702,901 and 902 can be known; Method among the present invention can have under aberration and the aberrationless situation; Effectively enlarge process window, promptly effectively improve the stability of etching system for technique change factors such as variation of exposure, out of focus, scalar aberration and Polarization aberration.

Though in conjunction with accompanying drawing embodiment of the present invention has been described; But to those skilled in the art; Under the prerequisite that does not break away from the principle of the invention, can also make some distortion, replacement and improvement, these also should be regarded as belonging to protection scope of the present invention.

Claims (3)

1. optimization method based on the imperfect etching system OPC of Abbe vector imaging model is characterized in that concrete steps are:

Step 101, mask pattern M is initialized as size is the targeted graphical of N * N

;

Step 102, the transmissivity that initial mask pattern M upper shed part is set are 1, and the transmissivity in resistance light zone is 0; Set the matrix of variables Ω of N * N: as M (x; O'clock y)=1;

is as M (x; O'clock y)=0;

be M (x, y) transmissivity of each pixel on the expression mask pattern wherein;

Step 103, objective function D is configured to the imaging evaluation function D at desirable image planes place ₁With defocusing amount be the imaging evaluation function D at f image planes place ₂Linear combination, i.e. D=η D ₁+ (1-η) D ₂, wherein, η ∈ (0,1) is a weighting coefficient;

Imaging evaluation function D ₁Be set at aerial image and the Euler's distance between the targeted graphical behind the amplitude modulation(PAM) on the desirable image planes square, promptly

Wherein

Be the pixel value of targeted graphical, I _Nom(x is the pixel value of the aerial image on the corresponding desirable image planes of current mask y), and ω ∈ (0,1) is an amplitude modulation coefficient;

Imaging evaluation function D ₂Be set at defocusing amount and be aerial image and the Euler's distance between the targeted graphical behind the amplitude modulation(PAM) on the f image planes square, promptly

I wherein _Off(x is the pixel value of the aerial image on the f image planes for the corresponding defocusing amount of current mask y);

Aerial image on the corresponding projection objective image planes of wherein current mask and the corresponding defocusing amount of current mask are that the acquisition process of the aerial image on the f image planes is:

Step 201, mask pattern M grid is turned to N * N sub regions;

Step 202, surface of light source is tiled into a plurality of pointolites, with each grid region center point coordinate (x _s, y _s) represent the pairing pointolite coordinate of this grid region;

Step 203, according to required obtain residing image planes of aerial image and desirable image planes apart from δ, obtain the variable quantity ξ of the etching system incident light phase place that causes by said δ; Wherein to the aerial image on the desirable image planes, then δ=0 is the aerial image on the f image planes, then δ=f to defocusing amount;

Step 204, obtain the scalar aberration matrix W of describing optical projection system scalar aberration (α '; β ') and describe the Polarization aberration matrix J (α ', β ') of optical projection system Polarization aberration, wherein (α '; β ', γ ') be that global coordinate system carries out the coordinate system behind the Fourier transform on the image planes;

Step 205, to a single point light source, utilize its coordinate (x _s, y _s), the variable quantity ξ of incident light phase place, scalar aberration matrix W (α ', β ') and Polarization aberration matrix J (α ', β '), when obtaining this spot light, the aerial image I on the desirable image planes _Nom(α _s, β _s) and defocusing amount be the aerial image I on the f image planes _Off(α _s, β _s);

Step 206, judge whether to calculate the corresponding aerial image I of all pointolites _Nom(α _s, β _s) and I _Off(α _s, β _s), if then get into step 207, otherwise return step 205;

Step 207, according to the Abbe method, the aerial image I corresponding to each pointolite _Nom(α _s, β _s) superpose, obtain the aerial image I on the desirable image planes _Nom, the aerial image I corresponding to each pointolite _Off(α _s, β _s) superpose, obtain the aerial image I on the image planes that defocusing amount is f _Off

Step 104, calculating target function D are for the gradient matrix

of matrix of variables Ω;

Step 105, utilize steepest prompt drop method to upgrade matrix of variables to be Ω '; Promptly

wherein s be predefined optimization step-length, obtain the mask pattern

of corresponding current Ω '

Step 106, calculate the corresponding target function value D of current mask pattern

; When D reaches predetermined upper limit value less than predetermined threshold or the number of times that upgrades matrix of variables Ω, get into step 107, matrix of variables Ω is that Ω ' returns step 104 otherwise make;

Step 107; Stop to optimize, and be targeted graphical horizontal direction cycle and the smaller of vertical direction in the cycle with the length of side of the said square window of core

of the current mask pattern of square window intercepting

;

Step 108; To

in the horizontal direction with the enterprising line period property continuation of vertical direction; Mask size after continuation is decided to be the figure

that obtains this moment through the mask pattern after optimizing more than or equal to the targeted graphical size.

2. according to the said optimization method of claim 1, it is characterized in that, in the said step 205, the aerial image I that the acquisition point light source is corresponding _Nom(α _s, β _s) and I _Off(α _s, β _s) detailed process be:

The setting global coordinate system is: the direction with optical axis is the z axle, and according to the left-handed coordinate system principle with the z axle set up global coordinate system (x, y, z);

Step 301, according to pointolite coordinate (x _s, y _s), the light wave that the calculation level light source sends is through the near field distribution E of N * N sub regions on the mask; Wherein, E is the vector matrix of N * N, and its each element is one 3 * 1 vector, 3 components of the diffraction near field distribution of mask in the expression global coordinate system;

Step 302, according near field distribution E obtain light wave the Electric Field Distribution

at optical projection system entrance pupil rear wherein

be the vector matrix of N * N; Its each element is one 3 * 1 vector, 3 components of the Electric Field Distribution at entrance pupil rear in the expression global coordinate system;

Step 303, to establish light wave direction of propagation in optical projection system approximate parallel with optical axis; Further according to Electric Field Distribution

the scalar aberration matrix W at entrance pupil rear (α '; β ') and the Polarization aberration matrix J (α '; β '); Obtain light wave wherein in the Electric Field Distribution

in optical projection system emergent pupil the place ahead; The Electric Field Distribution in emergent pupil the place ahead

is the vector matrix of N * N; Its each element is one 3 * 1 vector, 3 components of the Electric Field Distribution in emergent pupil the place ahead in the expression global coordinate system;

Step 304, the exit pupil of the projection system according to the front of the electric field distribution

Get behind the exit pupil of the projection system of the electric field distribution

Step 305, utilize Wolf Wolf optical imagery theoretical, according to the Electric Field Distribution at emergent pupil rear

And the variable quantity ξ of incident light phase place, obtain the Electric Field Distribution on the desirable image planes

With defocusing amount be the Electric Field Distribution on the f image planes

And according to

Aerial image I on the desirable image planes of acquisition point light source correspondence _Nom(α _s, β _s), according to

The defocusing amount that the acquisition point light source is corresponding is the aerial image I on the f image planes _Off(α _s, β _s).

3. according to the said optimization method of claim 1; It is characterized in that; In the said step 202 surface of light source being tiled into a plurality of pointolites is: with being parallel to the equally spaced straight line of X axle and Y direction, the surface of light source grid of partial coherence light source is turned to the equal little square of size.

Images