CN201083963Y - Photo-etching machine projection objective coma in situ detection system - Google Patents

Abstract

The utility model relates to a coma in-situ detection system for lithography tool projection lens comprising a light source, a lighting system, a test mask, a mask stage, projection lens, a workpiece-stage, an image sensing device data acquisition card and a computer; wherein the image sensing device data acquisition card and the computer is arranged on the wokpiece-stage. The image sensing device comprises an aperture stop, objective lens and a photodetector. The test mask comprises two perpendicular phase-shifting grating mask indicators with lower linewidth and two perpendicular binary grating indicators with larger linewidth. The utility model has the advantages that the influence on the image position offset caused by distortion can be eliminated and the coma in situ precision is improved.

Description

Photo-etching machine projecting objective coma aberration in situ detection system

Technical field

The utility model relates to litho machine, particularly a kind of photo-etching machine projecting objective coma aberration in situ detection system.

Background technology

Make the field at great scale integrated circuit, the advanced scanning projecting photoetching machine that is used for photoetching process is known.Projection objective system is one of most important subsystem in the advanced scanning projecting photoetching machine.The aberration of projection objective makes the optical patterning deterioration of litho machine, and causes reducing of photoetching process tolerance limit.The coma of projection objective makes the graph exposure on the mask behind silicon chip the image space skew take place, and this imaging offset is relevant with dimension of picture and lighting condition, thereby the coma of projection objective is one of key factor that influences alignment precision.Coma also can cause the symmetric figure on the mask asymmetric at the figure that exposure, the back of developing form on silicon chip, thereby influences the homogeneity of photoetching resolution and live width.Along with constantly reducing of lithographic feature size, the use of especially various resolution enhance technology, coma is more and more outstanding to the influence of optical patterning quality.Therefore, quick, high-precision photo-etching machine projecting objective coma aberration in situ detection system and detection method are indispensable.

TAMIS (TIS At Multiple Illumination Settings) technology is to be used to one of major technique that detects photo-etching machine projecting objective coma aberration at present in the world.(referring to technology formerly, Hans van der Laan, MarcelDierichs, Henk van Greevenbroek, Elaine McCoo, Fred Stoffels, Richard Pongers, RobWillekers. " Aerial image measurement methods for fast aberration set-up and illuminationpupil verification. " Proc.SPIE 2001,4346,394-407.) system that adopts of TAMIS technology comprises work stage and is installed in transmission-type image-position sensor on the work stage, mask platform and test mask, illuminator and computing machine etc.Wherein the transmission-type image-position sensor is made of two parts: a cover is of a size of isolated line and square hole of submicron order, and independently photodiode is all placed in isolated line and square hole below.Wherein isolated line comprises the isolated line of directions X and the isolated line of Y direction, and square hole is used for the light-intensity variation of compensating illumination light source.The transmission-type image-position sensor can be distinguished the image space of measured X direction lines and Y direction lines.In the TAMIS technology, make by the travelling workpiece platform that test badge can obtain the image space (X of mark through the projection objective imaging on the transmission-type image-position sensor scanning mask, Y), again with the ideal image position obtain after relatively imaging offset (Δ X (and NA, σ), Δ Y (NA, σ)).In different projection objective numerical apertures and illuminator partial coherence factor the image space of measuring each mark on the mask down is set, obtains the imaging offset Δ X (NA at diverse location place in the visual field under the different lighting conditions _i, σ _i), Δ Y (NA _i, σ _i), (i=1,2,3 ... n), obtain the corresponding zernike coefficient Z of coma after utilizing mathematical model to calculate then ₇, Z ₈, Z ₁₄, Z ₁₅

Because the transmission-type image-position sensor has special structure, so the shape of test badge generally need be designed to the shape of certain branch of transmission-type image-position sensor, so the design of test badge has been subjected to certain restriction.In addition, in the measuring process of imaging offset, need make on the transmission image-position sensor scanning mask test badge through the projection objective imaging by the travelling workpiece platform, so Measuring Time be longer relatively.

The test mask that the TAMIS technology adopts is a binary mask, and with respect to various phase shifting masks, coma is less to the influence of binary mask image space skew.Therefore the TAMIS technology uses binary mask to carry out the coma detection, and the variation range of sensitivity coefficient is less, and the precision that causes coma to detect is limited.

Distortion is one of main vertical axial aberration of projection lens of lithography machine, and distortion can cause the graph exposure on the mask behind silicon chip the image space skew to take place equally.Do not consider the influence of distortion during TAMIS commercial measurement coma, thereby make the coma detection have certain error, influenced the precision that coma detects imaging offset.In addition, in the TAMIS technology coma testing process, must be simultaneously to Z ₂, Z ₃Carry out The Fitting Calculation, therefore influenced the speed that coma detects.Along with constantly reducing of lithographic feature size, need more the photo-etching machine projecting objective coma aberration in situ detection system and the detection method of high precision, more speed.

Summary of the invention

The purpose of this utility model is to provide a kind of photo-etching machine projecting objective coma aberration in situ detection system, and the utility model will be eliminated the influence that distortion detects coma, improves the precision that coma detects.

Technical solution of the present utility model is as follows:

A kind of photo-etching machine projecting objective coma aberration in situ detection system, comprise light source, on the output light path of this light source, be illuminator successively with optical axis ground, test mask, the mask platform of bearing test mask, projection objective, work stage and be installed on this work stage the picture sensing device, this links to each other with computing machine by data collecting card as sensing device, it is characterized in that described test mask is by the less x direction coma measurement markers of live width, y direction coma measurement markers, x direction coma reference marker that live width is bigger and y direction coma reference marker constitute, described x direction coma measurement markers and y direction coma measurement markers are phase shift grating markers, described x direction coma reference marker and y direction coma reference marker are the binary raster marks, describedly comprise aperture diaphragm as sensing device, image-forming objective lens and photodetector, described photodetector links to each other with computing machine by data collecting card.

Phase shift grating marker as described x direction coma measurement markers and y direction coma measurement markers can be the alternate type phase shift grating marker, or the attenuation type phase shift grating marker, or the Chrome-free phase shift grating marker.

Described photodetector is CCD, or photodiode array.

Utilize above-mentioned photo-etching machine projecting objective coma aberration in situ detection system to carry out the method for photo-etching machine projecting objective coma aberration in situ detection, may further comprise the steps:

1. start light source, the test mask of the illumination light that light source sends on illuminator irradiation mask platform, x direction coma measurement markers on this test mask, y direction coma measurement markers, x direction coma reference marker, y direction coma reference marker through the picture of projection objective by aperture diaphragm filtering after image-forming objective lens be imaged on the test surface of photodetector and be converted into electric signal, this electric signal is sent into computing machine after by the data collecting card collection and is carried out data processing, obtain under current numerical aperture NA and partial coherence factor σ condition, relative imaging offset Δ X (NA between the center of x direction coma measurement markers aerial image and the center of x direction coma reference marker aerial image, σ), and the relative imaging offset Δ Y between the center of the center of y direction coma measurement markers aerial image and y direction coma reference marker aerial image (NA, σ):

ΔX(NA，σ)＝ΔX ₃₁(NA，σ)-ΔX ₃₂(NA，σ)

ΔY(NA，σ)＝ΔY ₃₃(NA，σ)-ΔY ₃₄(NA，σ)

Wherein: Δ X ₃₁(NA, σ), Δ X ₃₂(NA, σ), Δ Y ₃₃(NA, σ), Δ Y ₃₄(NA σ) is respectively x direction coma measurement markers, x direction coma reference marker, y direction coma measurement markers and the imaging offset of y direction coma reference marker behind projection objective on the test mask;

2. the partial coherence factor σ by changing illuminator and the numerical aperture NA of projection objective utilize describedly to record the relative imaging offset Δ X (NA of many groups as sensing device _i, σ _i), Δ Y (NA _i, σ _i), (i=1,2,3 ... n), wherein n is that lighting parameter is provided with number, and the value of n is determined that by measuring accuracy then the n value is big for the measuring accuracy height;

3. utilize lithography simulation software to demarcate the coma sensitivity coefficient of described projection objective under different numerical aperture NA and partial coherence factor σ condition:

$S_1({\mathrm{NA}}_i,{\mathrm{\σ}}_i)=\frac{\∂\mathrm{\ΔX}({\mathrm{NA}}_i,{\mathrm{\σ}}_i)}{{\∂Z}_7}(i=\mathrm{1,2,3}......n),$

$S_2({\mathrm{NA}}_i,{\mathrm{\σ}}_i)=\frac{\∂\mathrm{\ΔX}({\mathrm{NA}}_i,{\mathrm{\σ}}_i)}{{\∂Z}_{14}}(i=\mathrm{1,2,3}......n),$

$S_3({\mathrm{NA}}_i,{\mathrm{\σ}}_i)=\frac{\∂\mathrm{\ΔY}({\mathrm{NA}}_i,{\mathrm{\σ}}_i)}{{\∂Z}_8}(i=\mathrm{1,2,3}......n),$

$S_4({\mathrm{NA}}_i,{\mathrm{\σ}}_i)=\frac{\∂\mathrm{\ΔY}({\mathrm{NA}}_i,{\mathrm{\σ}}_i)}{{\∂Z}_{15}}(i=\mathrm{1,2,3}......n),$

Wherein: Δ (NA _i, σ _i) and Δ Y (NA _i, σ _i) be different numerical apertures with partial coherence factor under relative imaging offset, Z ₇, Z ₈, Z ₁₄And Z ₁₅Be the zernike coefficient of expression coma, scaling method is as follows:

As the sensitivity coefficient S that demarcates under certain numerical aperture and partial coherence factor condition ₁(NA _i, σ _i) time, set certain Z earlier ₇Value and to get other zernike coefficient be zero uses the lithography simulation software emulation to calculate the relative position offset X (NA that is caused by directions X three rank comas _i, σ _i), Ci Shi sensitivity coefficient S then ₁(NA _i, σ _i) be Δ X (NA _i, σ _i) and Z ₇The ratio;

Demarcate S with quadrat method ₂(NA _i, σ _i), S ₃(NA _i, σ _i) and S ₄(NA _i, σ _i);

4. the relative imaging offset Δ X (NA that under different numerical aperture NA and partial coherence factor σ condition, records _i, σ _i), Δ Y (NA _i, σ _i) (i=1,2,3 ... n) with sensitivity coefficient S ₁(NA _i, σ _i), S ₂(NA _i, σ _i), S ₃(NA _i, σ _i), S ₄(NA _i, σ _i) and the zernike coefficient Z that characterizes coma ₇, Z ₈, Z ₁₄, Z ₁₅Between relation be expressed from the next:

$\left[\begin{array}{c}\mathrm{\&Delta;X}({\mathrm{NA}}_1,{\mathrm{\&sigma;}}_1)\\ \mathrm{\&Delta;X}({\mathrm{<figure-callout\; id="2"\; label="NA"\; filenames="S2007200739733E00011.png"\; state="\{\{state\}\}">NA</figure-callout>}}_2,{\mathrm{\&sigma;}}_2)\\ .\\ .\\ .\end{array}\right]=\left[\begin{array}{cc}{S}_1({\mathrm{NA}}_1,{\mathrm{\&sigma;}}_1)& S_2({\mathrm{NA}}_1,{\mathrm{\&sigma;}}_1)\\ S_1({\mathrm{<figure-callout\; id="2"\; label="NA"\; filenames="S2007200739733E00011.png"\; state="\{\{state\}\}">NA</figure-callout>}}_2,{\mathrm{\&sigma;}}_2)& S_2({\mathrm{<figure-callout\; id="2"\; label="NA"\; filenames="S2007200739733E00011.png"\; state="\{\{state\}\}">NA</figure-callout>}}_2,{\mathrm{\&sigma;}}_2)\\ .& .\\ .& .\\ .& .\end{array}\right]\left[\begin{array}{c}{Z}_7\\ Z_{14}\end{array}\right]$

$\left[\begin{array}{c}\mathrm{\&Delta;Y}({\mathrm{NA}}_1,{\mathrm{\&sigma;}}_1)\\ \mathrm{\&Delta;Y}({\mathrm{<figure-callout\; id="2"\; label="NA"\; filenames="S2007200739733E00011.png"\; state="\{\{state\}\}">NA</figure-callout>}}_2,{\mathrm{\&sigma;}}_2)\\ .\\ .\\ .\end{array}\right]=\left[\begin{array}{cc}{S}_3({\mathrm{NA}}_1,{\mathrm{\&sigma;}}_1)& S_4({\mathrm{NA}}_1,{\mathrm{\&sigma;}}_1)\\ S_3({\mathrm{<figure-callout\; id="2"\; label="NA"\; filenames="S2007200739733E00011.png"\; state="\{\{state\}\}">NA</figure-callout>}}_2,{\mathrm{\&sigma;}}_2)& S_4({\mathrm{<figure-callout\; id="2"\; label="NA"\; filenames="S2007200739733E00011.png"\; state="\{\{state\}\}">NA</figure-callout>}}_2,{\mathrm{\&sigma;}}_2)\\ .& .\\ .& .\\ .& .\end{array}\right]\left[\begin{array}{c}{Z}_8\\ Z_{15}\end{array}\right]$

Utilize least square method to find the solution above-mentioned two formulas, can obtain the zernike coefficient Z relevant with the coma of projection objective (5) ₇, Z ₈, Z ₁₄And Z ₁₅

5. pass through the main control computer travelling workpiece platform of litho machine, x direction coma measurement markers on the test mask, y direction coma measurement markers, x direction coma reference marker and y direction coma reference marker are moved to the diverse location of the pupil plane of projection objective, 1.～4. repeating step characterizes the zernike coefficient Z of projection objective diverse location coma with measurement ₇, Z ₈, Z ₁₄And Z ₁₅

It is 30～60 that described lighting parameter is provided with the general span of several n.

The utility model is compared with technology formerly, has the following advantages and good effect:

1. the utility model can be eliminated the influence of distortion to imaging offset by the measurement of the relative imaging offset of test badge, thereby has improved the precision that coma detects.

2. adopted phase shift grating marker in the test mask of the present utility model, more responsive to coma, can improve the precision that coma detects.

3. during the utility model measurement markers relative position side-play amount, need not to make on the transmission image-position sensor scanning mask test badge through the projection objective imaging by the travelling workpiece platform, can directly write down on the mask test badge through the light distribution of projection objective imaging, thereby calculate the relative imaging offset of test badge.

Description of drawings

Fig. 1 is the structural representation of the utility model photo-etching machine projecting objective coma aberration in situ detection system.

Fig. 2 is the synoptic diagram of the test badge on the utility model institute use test mask.

Fig. 3 is the picture sensing device structural representation that the utility model adopts.

State 4 is under the traditional lighting condition, the Z of the test badge that adopts among the utility model embodiment ₇Relation between sensitivity coefficient and numerical aperture, the partial coherence factor.

Fig. 5 is under the ring illumination condition, the Z of the test badge that adopts among the utility model embodiment ₇Relation between sensitivity coefficient and numerical aperture, the partial coherence factor.

Fig. 6 is under the traditional lighting condition, the Z of the intensive line markings in the TAMIS technology ₇Relation between sensitivity coefficient and numerical aperture, the partial coherence factor.

Fig. 7 is under the ring illumination condition, the Z of the intensive line markings in the TAMIS technology ₇Relation between sensitivity coefficient and numerical aperture, the partial coherence factor.

Fig. 8 is under the traditional lighting condition, the Z of the test badge that adopts among the utility model embodiment ₁₄Relation between sensitivity coefficient and numerical aperture, the partial coherence factor.

Fig. 9 is under the ring illumination condition, the Z of the test badge that adopts among the utility model embodiment ₁₄Relation between sensitivity coefficient and numerical aperture, the partial coherence factor.

Figure 10 is under the traditional lighting condition, the Z of the intensive line markings in the TAMIS technology ₁₄Relation between sensitivity coefficient and numerical aperture, the partial coherence factor.

Figure 11 is under the ring illumination condition, the Z of the intensive line markings in the TAMIS technology ₁₄Relation between sensitivity coefficient and numerical aperture, the partial coherence factor.

Embodiment

The utility model is described in further detail below in conjunction with embodiment and accompanying drawing, but should not limit protection domain of the present utility model with this.

See also Fig. 1 earlier, Fig. 1 is the structural representation of the utility model photo-etching machine projecting objective coma aberration in situ detection system.As seen from the figure, the utility model photo-etching machine projecting objective coma aberration in situ detection system, comprise light source 1, on the output beam of this light source 1, be illuminator 2 successively with optical axis ground, test mask 3, the mask platform 4 of bearing test mask 3, projection objective 5, work stage 6 and be installed on this work stage 6 the picture sensing device 7, this links to each other with computing machine 9 by data collecting card 8 as sensing device 7, be characterized in that described test mask 3 is by the less x direction coma measurement markers 31 of live width, y direction coma measurement markers 33, x direction coma reference marker 32 that live width is bigger and y direction coma reference marker 34 constitute, described x direction coma measurement markers 31 and y direction coma measurement markers 33 are phase shift grating markers, described x direction coma reference marker 32 and y direction coma reference marker 34 are binary raster marks, describedly comprise aperture diaphragm 71 as sensing device 7, image-forming objective lens 72 and photodetector 73, described photodetector 73 links to each other with computing machine 9 by data collecting card 8.

Described light source 1 produces illuminating bundle; Described illuminator 2 is used to adjust beam waist, light distribution, partial coherence factor and the lighting system of the light beam that described light source sends; Described mask platform 4 can also accurately be located by bearing test mask 3; Described projection objective 5 can be adjustable with pattern imaging on the test mask 3 and numerical aperture; Work stage 6 can accurately be located; The described pattern imaging position that is used to measure on this work stage 6 on the test mask 3 that is installed in as sensing device 7; Described data collecting card 8 is used for measuring-signal and gathers in real time; Described computing machine 9 is used for Data Management Analysis.

Described light source 1 can be ultraviolet, deep ultraviolet and extreme ultraviolet light sources such as mercury lamp, excimer laser, laser plasma light source and discharge plasma light source.

Described illuminator 2 comprises extender lens group 21, beam shaping 22 and beam homogenizer 23.

Described lighting system comprises traditional lighting, ring illumination, secondary illumination, level Four illumination etc.

As shown in Figure 2, comprise live width less x direction coma measurement markers 31, y direction coma measurement markers 33 and live width bigger x direction coma reference marker 32, y direction coma reference marker 34 on the described test mask 3.

Described x direction coma measurement markers 31 and y direction coma measurement markers 33 can be the alternate type phase shift grating markers, attenuation type phase shift grating marker, Chrome-free phase shift grating marker etc.

Described x direction coma reference marker 32 and y direction coma reference marker 34 are binary raster marks.

Described projection objective 5 can be total transmissivity formula projection objective, catadioptric formula projection objective, total-reflection type projection objective etc.

As shown in Figure 3, describedly comprise aperture diaphragm 71 as sensing device 7, image-forming objective lens 72, photodetector 73 etc.

Described photodetector 73 can be that CCD, photodiode array or other have the detector array of photosignal translation function.During measurement markers relative position side-play amount, need not to make on the transmission image-position sensor scanning mask test badge through the projection objective imaging by the travelling workpiece platform, can directly write down on the mask test badge through the light distribution of projection objective imaging, thereby calculate the relative imaging offset of test badge.

Utilize the utility model photo-etching machine projecting objective coma aberration in situ detection system to carry out the detection method of photo-etching machine projecting objective coma aberration original position, may further comprise the steps:

Start litho machine, the extender lens group 21 of the illumination light that light source 1 sends in illuminator 2 expands Shu Houjin and goes into light beam reshaper 22, obtains needed lighting system, enters the light intensity homogenising that beam homogenizer 23 makes illumination light again; Test mask 3 on the illumination beam mask platform 4 after the light intensity homogenising,

Make x direction coma measurement markers 31, y direction coma measurement markers 33, x direction coma reference marker 32, y direction coma reference marker 34 on the test mask 3 be imaged on aperture diaphragm 71 surfaces on the picture sensing device 7 that is installed in work stage 6 through projection objective 5 by travelling workpiece platform 6; X direction coma measurement markers 31, y direction coma measurement markers 33, x direction coma reference marker 32, the picture of y direction coma reference marker 34 by aperture diaphragm 71 filtering after image-forming objective lens 72 be imaged on photodetector 73 surface and be converted into electric signal, send into computing machine 9 after this signal is gathered by data collecting card 8 and carry out data processing, can be under current numerical aperture NA and partial coherence factor σ condition by calculating, relative imaging offset Δ X (NA between the center of x direction coma measurement markers 31 aerial images and the center of x direction coma reference marker 32 aerial images, σ), and the relative imaging offset Δ Y between the center of the center of y direction coma measurement markers 33 aerial images and y direction coma reference marker 34 aerial images (NA, σ); The numerical aperture of partial coherence factor, lighting system and projection objective 5 by changing illuminator 2 is utilized describedly to record the described relative imaging offset Δ X (NA of many groups as sensing device 7 _i, σ _i), Δ Y (NA _i, σ _i), (i=1,2,3 ... n); Utilize lithography simulation software to demarcate the coma sensitivity coefficient S of described projection objective 5 under different numerical apertures and partial coherence factor condition ₁(NA, σ) and S ₂(NA, σ); Utilize described coma sensitivity coefficient to calculate the size of the zernike coefficient relevant with the coma of projection objective 5.Detailed demarcation and calculation process are as described below.

The wave aberration of projection objective is represented by zernike polynomial usually:

$W(\mathrm{\&rho;},\mathrm{\&theta;})=\underset{n=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{Z}_n\&CenterDot;R_n(\mathrm{\&rho;},\mathrm{\&theta;})$

$=Z_1+{\mathrm{<figure-callout\; id="2"\; label="Z"\; filenames="S2007200739733E00011.png"\; state="\{\{state\}\}">Z</figure-callout>}}_2\mathrm{\&rho;}\cos \mathrm{\&theta;}+{\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="S2007200739733E00011.png"\; state="\{\{state\}\}">Z</figure-callout>}}_3\mathrm{\&rho;}\sin \mathrm{\&theta;}+Z_4({2\mathrm{\&rho;}}^2-1)+{\mathrm{<figure-callout\; id="5"\; label="Z"\; filenames="S2007200739733E00011.png"\; state="\{\{state\}\}">Z</figure-callout>}}_5{\mathrm{\&rho;}}^2\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="S2007200739733E00011.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&theta;}+---\left(1\right)$

${\mathrm{<figure-callout\; id="6"\; label="Z"\; filenames="S2007200739733E00011.png"\; state="\{\{state\}\}">Z</figure-callout>}}_6{\mathrm{\&rho;}}^2\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="S2007200739733E00011.png"\; state="\{\{state\}\}">sin</figure-callout>}2\mathrm{\&theta;}+Z_7({3\mathrm{\&rho;}}^2-2)\mathrm{\&rho;}\cos \mathrm{\&theta;}+Z_8({3\mathrm{\&rho;}}^2-2)\mathrm{\&rho;}\sin \mathrm{\&theta;}+...+$

$Z_{14}({10\mathrm{\&rho;}}^4-{12\mathrm{\&rho;}}^2+3)\mathrm{\&rho;}\cos \mathrm{\&theta;}+Z_{15}({10\mathrm{\&rho;}}^4-{12\mathrm{\&rho;}}^2+3)\mathrm{\&rho;}\sin \mathrm{\&theta;}+...,$

Wherein: ρ, θ are the normalization polar coordinates of object lens emergent pupil face.Zernike coefficient Z ₂, with Z ₃Represent the wavetilt of directions X and Y direction respectively, Z ₇With Z ₈The three rank comas of representing directions X and Y direction respectively, Z ₁₄With Z ₁₅The five rank comas of representing directions X and Y direction respectively.Ignoring under the situation of higher order aberratons, the aberration function that influences the pattern imaging position offset can be expressed as:

W _X(ρ)＝Z ₂ρ+Z ₇(3ρ ³-2ρ)+Z ₁₄(10ρ ⁵-12ρ ³+3ρ)， (2)

W _Y(ρ)＝Z ₃ρ+Z ₈(3ρ ³-2ρ)+Z ₁₅(10ρ ⁵-12ρ ³+3ρ)， (3)

(2) linear term of ρ comprises fractional distortion in formula and (3) formula, and the existence of distortion makes the coma detection have certain error.The imaging offset that distortion causes does not change with the change of dimension of picture and density, and the imaging offset that coma causes depends on the size and the density of figure.Relative position offset X between x direction coma measurement markers 31 and the x direction coma reference marker 32 (NA, σ), and the relative imaging offset Δ Y between y direction coma measurement markers 33 and the y direction coma reference marker 34 (NA σ) can be expressed as

ΔX(NA，σ)＝ΔX ₃₁(NA，σ)-ΔX ₃₂(NA，σ)， (4)

ΔY(NA，σ)＝ΔY ₃₃(NA，σ)-ΔY ₃₄(NA，σ)。(5)

Wherein, Δ X ₃₁(NA, σ), Δ X ₃₂(NA, σ), Δ Y ₃₃(NA, σ), Δ Y ₃₄(NA σ) is respectively x direction coma measurement markers 31, x direction coma reference marker 32, y direction coma measurement markers 33, the position offset of y direction coma reference marker 34 after the projection objective imaging on the test mask 3.By the measurement of relative imaging offset, can eliminate the influence of (2) formula and (3) formula neutral line item, this relative imaging offset can be expressed as

ΔX(NA，σ)∝?Z ₇3ρ ³+Z ₁₄(10ρ ⁵-12ρ ³)， (6)

ΔY(NA，σ)∝?Z ₈3ρ ³+Z ₁₅(10ρ ⁵-12ρ ³)， (7)

By (6), (7) two formulas as can be known, the relative imaging offset that is caused by coma depends primarily on the distribution of the frequency spectrum of test badge at the projection objective pupil plane.It is high more to enter pupil non-zero order time diffraction light intensity, and the relative position side-play amount that coma causes is big more.Binary raster with respect to identical live width, the x direction coma measurement markers 31 and the y direction coma measurement markers 33 that comprise on the test mask 3 that the utility model adopts are phase shift grating marker, the order of diffraction that enters pupil is inferior more, and non-zero order diffraction light intensity is improved.Therefore the test badge that the utility model proposes will be more responsive to coma, be more suitable for coma and detect.

Meanwhile, the relative position side-play amount that causes of coma also depends on the partial coherence factor of the numerical aperture and the illuminator of projection objective.Under the certain situation of coma, change the numerical aperture of projection objective and the partial coherence factor of illuminator the light distribution of the light of different space frequency will be changed, thereby the relative position side-play amount that coma is caused changes.Regulate the partial coherence factor and the lighting system of beam shaping 22 change illuminators, and the numerical aperture of regulating projection objective 5, for x direction coma measurement markers 31 and x direction coma reference marker 32, and y direction coma measurement markers 33 and y direction coma reference marker 34 have respectively

ΔX(NA _i，σ _i)＝S ₁(NA _i，σ _i)Z ₇+S ₂(NA _i，σ _i)Z ₁₄(i＝1，2，3……n)， (8)

ΔY(NA _i，σ _i)＝S ₃(NA _i，σ _i)Z ₈+S ₄(NA _i，σ _i)Z ₁₅(i＝1，2，3……n)， (9)

Wherein, Δ X (NA _i, σ _i) the x direction coma measurement markers 31 that causes for coma under given numerical aperture NA and partial coherence factor σ condition and the relative imaging offset of x direction coma reference marker 32, Δ Y (NA _i, σ _i) the y direction coma measurement markers 33 that causes for coma under given numerical aperture NA and partial coherence factor σ condition and the relative imaging offset of y direction coma reference marker 34.S ₁(NA _i, σ _i), S ₂(NA _iσ _i), S ₃(NA _i, σ _i) and S ₄(NA _i, σ _i) be the coma sensitivity coefficient, by following formula definition

$S_1({\mathrm{NA}}_i,{\mathrm{\&sigma;}}_i)=\frac{\&PartialD;\mathrm{\&Delta;X}({\mathrm{NA}}_i,{\mathrm{\&sigma;}}_i)}{{\&PartialD;Z}_7}(i=\mathrm{1,2,3}......n),---\left(10\right)$

$S_2({\mathrm{NA}}_i,{\mathrm{\&sigma;}}_i)=\frac{\&PartialD;\mathrm{\&Delta;X}({\mathrm{NA}}_i,{\mathrm{\&sigma;}}_i)}{{\&PartialD;Z}_{14}}(i=\mathrm{1,2,3}......n),---\left(11\right)$

$S_3({\mathrm{NA}}_i,{\mathrm{\&sigma;}}_i)=\frac{\&PartialD;\mathrm{\&Delta;Y}({\mathrm{NA}}_i,{\mathrm{\&sigma;}}_i)}{{\&PartialD;Z}_8}(i=\mathrm{1,2,3}......n),---\left(12\right)$

$S_4({\mathrm{NA}}_i,{\mathrm{\&sigma;}}_i)=\frac{\&PartialD;\mathrm{\&Delta;Y}({\mathrm{NA}}_i,{\mathrm{\&sigma;}}_i)}{{\&PartialD;Z}_{15}}(i=\mathrm{1,2,3}......n),---\left(13\right)$

Sensitivity coefficient changes with the numerical aperture of projection objective and the partial coherence factor of illuminator, can utilize lithography simulation software to demarcate and obtain.As demarcating the sensitivity coefficient S under certain numerical aperture and partial coherence factor condition ₁(NA _i, σ _i) time, can set certain Z7 value and get other zernike coefficient is zero, uses the lithography simulation software emulation to calculate the relative position offset X (NA that is caused by directions X three rank comas _i, σ _i), Ci Shi sensitivity coefficient S then ₁(NA _i, σ _i) can be Δ X (NA _i, σ _i) and Z ₇Ratio, S ₂(NA _i, σ _i), S ₃(NA _i, σ _i) and S ₄(NA _i, σ _i) scaling method and S ₁(NA _i, σ _i) similar.

Be provided with down in a series of different numerical apertures and partial coherence factor, by being installed in x direction coma measurement markers 31 and x direction coma reference marker 32 on the picture sensing device 7 probing test masks 3 on the work stage 6, and y direction coma measurement markers 33 can obtain its light distribution and calculate relative imaging offset with the aerial image of y direction coma reference marker 34, can be represented by following matrix equation:

$\left[\begin{array}{c}\mathrm{\&Delta;X}({\mathrm{NA}}_1,{\mathrm{\&sigma;}}_1)\\ \mathrm{\&Delta;X}({\mathrm{<figure-callout\; id="2"\; label="NA"\; filenames="S2007200739733E00011.png"\; state="\{\{state\}\}">NA</figure-callout>}}_2,{\mathrm{\&sigma;}}_2)\\ .\\ .\\ .\end{array}\right]=\left[\begin{array}{cc}{S}_1({\mathrm{NA}}_1,{\mathrm{\&sigma;}}_1)& S_2({\mathrm{NA}}_1,{\mathrm{\&sigma;}}_1)\\ S_1({\mathrm{<figure-callout\; id="2"\; label="NA"\; filenames="S2007200739733E00011.png"\; state="\{\{state\}\}">NA</figure-callout>}}_2,{\mathrm{\&sigma;}}_2)& S_2({\mathrm{<figure-callout\; id="2"\; label="NA"\; filenames="S2007200739733E00011.png"\; state="\{\{state\}\}">NA</figure-callout>}}_2,{\mathrm{\&sigma;}}_2)\\ .& .\\ .& .\\ .& .\end{array}\right]\left[\begin{array}{c}{Z}_7\\ Z_{14}\end{array}\right],---\left(14\right)$

$\left[\begin{array}{c}\mathrm{\&Delta;Y}({\mathrm{NA}}_1,{\mathrm{\&sigma;}}_1)\\ \mathrm{\&Delta;Y}({\mathrm{<figure-callout\; id="2"\; label="NA"\; filenames="S2007200739733E00011.png"\; state="\{\{state\}\}">NA</figure-callout>}}_2,{\mathrm{\&sigma;}}_2)\\ .\\ .\\ .\end{array}\right]=\left[\begin{array}{cc}{S}_3({\mathrm{NA}}_1,{\mathrm{\&sigma;}}_1)& S_4({\mathrm{NA}}_1,{\mathrm{\&sigma;}}_1)\\ S_3({\mathrm{<figure-callout\; id="2"\; label="NA"\; filenames="S2007200739733E00011.png"\; state="\{\{state\}\}">NA</figure-callout>}}_2,{\mathrm{\&sigma;}}_2)& S_4({\mathrm{<figure-callout\; id="2"\; label="NA"\; filenames="S2007200739733E00011.png"\; state="\{\{state\}\}">NA</figure-callout>}}_2,{\mathrm{\&sigma;}}_2)\\ .& .\\ .& .\\ .& .\end{array}\right]\left[\begin{array}{c}{Z}_8\\ Z_{15}\end{array}\right].---\left(15\right)$

Above-mentioned equation is an overdetermined equation, can find the solution by least square method.Utilization is provided with following the measure x of diverse location place direction coma measurement markers 31 and x direction coma reference marker 32 in the visual field as sensing device 7 in series of values aperture and partial coherence factor, the relative imaging offset of y direction coma measurement markers 33 and y direction coma reference marker 34 utilizes the sensitivity coefficient of demarcating can calculate the zernike coefficient Z that characterizes relevant position coma in the visual field ₇, Z ₈, Z ₁₄And Z ₁₅

The system architecture of the utility model embodiment as shown in Figure 1, it is the ArF excimer laser of 193nm that light source 1 adopts wavelength, the lighting system that illuminator 2 provides is traditional lighting and ring illumination, wherein the partial coherence factor variation range of traditional lighting is 0.25～0.85, change step is 0.1, totally 7 kinds of partial coherence factor settings.The endless belt width of ring illumination is 0.3, and the variation range of endless belt core coherence factor is 0.3～0.8, and change step is 0.1, totally 6 kinds of partial coherence factor settings.The numerical aperture variation range of projection objective is 0.5～0.8, and change step is 0.05, totally 7 kinds of numerical aperture settings.Therefore in the present embodiment, conventional lighting system is got 49 kinds of lighting parameter settings altogether, and the ring illumination mode is got 42 kinds of lighting parameter settings altogether.X direction coma measurement markers 31 on the test mask 3 is the alternate type phase shift grating marker of 250nm for the live width of vertical direction, x direction coma reference marker 32 is the binary raster mark of 2 μ m for the live width of vertical direction, y direction coma measurement markers 31 is the alternate type phase shift grating marker of 250nm for the live width of horizontal direction, and y direction coma reference marker 32 is the binary raster mark of 2 μ m for the live width of horizontal direction.Projection objective 5 is total transmissivity formula projection objectives.Photodetector 73 among Fig. 3 is a photodiode array.

With x direction coma measurement markers 31 is example, and its multiple transmittance function is

$t\left(x\right)=\underset{n=-\&infin;}{\overset{+\&infin;}{\mathrm{\&Sigma;}}}\mathrm{\&delta;}(x-2\mathrm{np})*[\mathrm{rect}\left(\frac{x+p/2}{p/2}\right)-\mathrm{rect}\left(\frac{x-p/2}{p/2}\right)],---\left(16\right)$

Wherein, p is the pitch of alternate type moving phase grating.The alternate type moving phase grating is the Fourier transform of its multiple transmittance function in the spectrum distribution of objective lens pupil face:

$U\left(f_x\right)=\frac{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="S2007200739733E00011.png"\; state="\{\{state\}\}">j</figure-callout>}}{2}\underset{n=-\&infin;}{\overset{+\&infin;}{\mathrm{\&Sigma;}}}\mathrm{\&delta;}(f_x-\frac{n}{2p})\sin c\left(\frac{{\mathrm{pf}}_x}{2}\right)\sin \left({\mathrm{\&pi;pf}}_x\right),---\left(17\right)$

F wherein _x=sin θ/λ is the spatial frequency variable.The multiple transmittance function of x direction coma reference marker 32 is

$t\left(x\right)=\underset{n=-\&infin;}{\overset{+\&infin;}{\mathrm{\&Sigma;}}}\mathrm{\&delta;}(x-\mathrm{np})*\mathrm{rect}\left(\frac{x}{p/2}\right),---\left(18\right)$

Binary raster is the Fourier transform of its multiple transmittance function in the spectrum distribution of objective lens pupil face:

$U\left(f_x\right)=\frac{1}{2}\underset{n=-\&infin;}{\overset{+\&infin;}{\mathrm{\&Sigma;}}}\mathrm{\&delta;}(f_x-\frac{n}{p})\sin c\left(\frac{{\mathrm{pf}}_x}{2}\right).---\left(19\right)$

By (17) formula and (19) formula as can be known, the zero order diffracted light of alternate type phase shift grating marker lacks level, and the even level of binary raster except zero order diffracted light time diffraction light lacks level.For intensive line markings with identical live width, the alternate type moving phase grating has more than binary raster, and the diffraction light of multilevel enters objective lens pupil, and the diffraction spectra of alternate type moving phase grating does not contain DC component, the high order diffraction light intensity is improved, therefore, the alternate type moving phase grating is more responsive to coma, is more suitable for coma and detects.In the present embodiment, the relative imaging offset of alternate type phase shift grating marker with the binary raster mark of large-size by measuring less live width under different numerical apertures and partial coherence factor condition, utilization (14) calculates the zernike coefficient relevant with coma with (15) formula.

The variation range of sensitivity coefficient is the key factor that influences the coma accuracy of detection.Provide the simulation result of present embodiment coma sensitivity below.Fig. 4 and Fig. 5 are respectively under traditional lighting and the ring illumination condition, x direction coma measurement markers 31 on the utility model employing test mask 3 and the Z of the relative imaging offset Δ X of x direction coma reference marker 32 ₇Relation between sensitivity coefficient and numerical aperture, the partial coherence factor.Fig. 6 and Fig. 7 are respectively under traditional lighting and the ring illumination condition, the Z of TAMIS technology ₇Relation between sensitivity coefficient and numerical aperture, the partial coherence factor.The coma detection method that the utility model proposes is compared Z with the TAMIS technology ₇The variation range of sensitivity coefficient has increased 34.4% under the traditional lighting condition, increased 28.2% under the ring illumination condition.

Fig. 8 and Fig. 9 are respectively under traditional lighting and the ring illumination condition, x direction coma measurement markers 31 on the utility model employing test mask 3 and the Z of the relative position offset X of x direction coma reference marker 32 ₁₄Relation between sensitivity coefficient and numerical aperture, the partial coherence factor.Figure 10 and Figure 11 are respectively under traditional lighting and the ring illumination condition, the Z of TAMIS technology ₁₄Relation between sensitivity coefficient and numerical aperture, the partial coherence factor.The coma detection method that the utility model proposes is compared Z with the TAMIS technology ₁₄The variation range of sensitivity coefficient has increased 58.5% under the traditional lighting condition, increased 2.2% under the ring illumination condition.

By above explanation, compared with the prior art the utility model has eliminated distortion to the impact that coma detects, and carries The precision that high coma detects.

Claims (3)

1. photo-etching machine projecting objective coma aberration in situ detection system, comprise light source (1), on the output beam of this light source (1), be illuminator (2) successively with optical axis ground, test mask (3), the mask platform (4) of bearing test mask (3), projection objective (5), work stage (6) and be installed on this work stage (6) the picture sensing device (7), this links to each other with computing machine (9) by data collecting card (8) as sensing device (7), it is characterized in that described test mask (3) is by two x direction coma measurement markers (31) that mutually perpendicular live width is less, y direction coma measurement markers (33), constitute with two bigger x direction coma reference marker (32) and y direction coma reference markers (34) of orthogonal live width, described x direction coma measurement markers (31) and y direction coma measurement markers (33) are phase shift grating markers, described x direction coma reference marker (32) and y direction coma reference marker (34) are the binary raster marks, described picture sensing device (7) comprises aperture diaphragm (71), image-forming objective lens (72) and photodetector (73), described photodetector (73) links to each other with computing machine (9) by data collecting card (8).

2. photo-etching machine projecting objective coma aberration in situ detection according to claim 1 system, it is characterized in that phase shift grating marker as described x direction coma measurement markers (31) and y direction coma measurement markers (33), be the alternate type phase shift grating marker, or attenuation type phase shift grating marker, or Chrome-free phase shift grating marker.

3. photo-etching machine projecting objective coma aberration in situ detection according to claim 1 system is characterized in that described photodetector (73) is CCD, or photodiode array.

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