CN101949734B - Method for improving measurement precision of beam polarization degree - Google Patents

Abstract

The invention relates to a method for improving measurement precision of a beam polarization degree. A utilized polarization detection device comprises a phase delay device, an analyzer and a photo detector which are sequentially arranged along an optical axis of a system of the device, wherein the output of the photo detector is connected with a signal processing system, a beam to be measured which is parallel to the optical axis of the system is emitted to the phase delay device and the analyzer and detected by the photo detector, and the electric signal output by the photo detector is sent to the signal processing system for data processing. The method is characterized in that the transmission axis direction of the analyzer and the polarization direction of the beam to be measured are adjusted to be parallel or vertical according to the polarization direction of the beam to be measured, and then the measurement of the polarization degree of the beam to be measured is carried out. A stokes parameter and the polarization degree of the beam to be measured are obtained according to the light intensity detected by the photo detector. The invention can improve the measurement precision of the polarization degree.

Description

Improve the method for light beam polarization degree measuring accuracy

Technical field

The present invention relates to the detection of light beam polarization degree, particularly a kind of method that improves light beam polarization degree measuring accuracy.

Background technology

The progress of semiconductor fabrication is always with the power that is reduced into of the increase of the reducing of exposure wavelength, projection objective numerical aperture and photoetching process factor k1.Recent years, immersion lithography has been obtained fast development.In immersion lithography, adopt certain liquid filling between the photoresist on last a slice eyeglass of object lens and the silicon chip, make the numerical aperture of projection objective be significantly improved.When the numerical aperture of projection lens of lithography machine near 0.8 or when bigger, the illumination polarisation of light is very important to the influence of optical patterning.Adopting suitable polarized illumination is a kind of strong method that improves image contrast under the large-numerical aperture situation.For different lighting systems, the polarized light that the polarization illumination requirement has different linear polarization is as x direction polarized light, y direction polarized light, radial polarisation light, tangential polarization light etc.

When using polarized illumination, exist all multifactor meetings influence polarization state of light in the illuminator of litho machine.Most importantly the intrinsic birefringence of optical material and stress birefrin reduce the polarisation of light degree.In addition, the polarization characteristic of optical thin film, light also can influence polarisation of light in the reflection and the refraction at interface.Therefore, in the polarized illumination system,, should detect the polarization information of illumination light in real time owing to the needs of Polarization Control, and the rotating wave plate in the FEEDBACK CONTROL illuminator, assurance has the linearly polarized light output of high-polarization.In addition, also needing to carry out polarization illumination detects to be used for the dress school and the maintenance of litho machine.Formerly technology 1 (Jap.P.: Te Open 2005-005521) has proposed a kind of polarization parameter pick-up unit that utilizes rotatable phase delayer method.Fig. 2 is the synoptic diagram of illumination iris polarization parameter pick-up unit in the projection aligner that proposes of technology 1 formerly.As shown in Figure 2, this polarization parameter pick-up unit comprises pinhole mask 10, transform lens group 20, phase delay device 2 and driver 6 thereof, analyzer 3, photodetector 4 and signal processing system 5.Illuminating bundle by the pin hole 101 on the pinhole mask 10 after, become parallel beam through transform lens group 20.This parallel beam is surveyed by photodetector 4 by phase delay device 2 and analyzer 3 backs successively as light beam 1 to be measured.

Described pinhole mask 10 place projection aligner the mask face or near, perhaps with the plane of mask face conjugation or neighbouring (the silicon chip face or near, perhaps with the plane of silicon chip face conjugation or near).

When utilizing device in the technology 1 formerly to measure, the systematic optical axis rotation of phase delay device 2 winding apparatus, utilize technology 1 formerly and formerly the data processing method in the technology 2 (Jap.P.: Te Open 2006-179660) electric signal of photodetector output is handled, can obtain the Stokes' parameter and the degree of polarization of light beam to be measured.But phase delay device that this device is required and analyzer all are operated in the deep ultraviolet wave band, are difficult to make desirable device according to design objective at this wave band, therefore produce Stokes' parameter and degree of polarization measuring error.

For this reason, formerly technology 2 has proposed not to be subjected to the method that the influence of phase delay device and analyzer correlated error, high-precision measurement polarization state distribute.This method is to measure the polarization characteristic of each device before constituting device for testing polarization with phase delay device and analyzer, comprises the light transmission shaft direction, extinction ratio distribution of distribution in the face of phase delay device phase-delay quantity, quick shaft direction and analyzer etc.But this method not energy measurement constitutes the positioning error of the direction of the quick shaft direction of phase delay device behind the device for testing polarization and analyzer light transmission shaft.Therefore, when having the fast axle of phase delay device positioning error, analyzer light transmission shaft positioning error in the device for testing polarization, measurement result that will the polarisation-affecting degree.

Summary of the invention

Phase-delay quantity error, the light transmission shaft deflection error of quick shaft direction sum of errors analyzer, extinction ratio error for the phase delay device that reduces to produce in the device manufacturing processes, and the influence that the light transmission shaft direction positioning error of the quick shaft direction positioning error of phase delay device and analyzer is measured degree of polarization when constituting device for testing polarization, the present invention proposes a kind of method that improves light beam polarization degree measuring accuracy.This method can effectively reduce the influence of the above-mentioned error of phase delay device and analyzer to the degree of polarization measurement result by adjusting the direction of analyzer light transmission shaft.

Technical solution of the present invention is as follows:

A kind of method that improves light beam polarization degree measuring accuracy, the device for testing polarization that uses comprises the phase delay device that sets gradually along the apparatus system optical axis, analyzer and photodetector, the output of this photodetector connects signal processing system, but described phase delay device is the rotation of winding apparatus systematic optical axis under the driving of driver, parallel beam to be measured is incident to described phase delay device and analyzer in systematic optical axis, and by described photodetector detection, the electric signal of this photodetector output is sent into described signal processing system and is carried out data processing, its characteristics are, polarization direction according to described light beam to be measured, adjust the light transmission shaft direction of described analyzer parallel with the polarization direction of described light beam to be measured or vertical after, carry out the measurement of the degree of polarization of light beam to be measured again.

When generally knowing the polarization direction of light beam to be measured, its concrete measuring process is as follows:

1. the light transmission shaft direction of adjusting described analyzer is parallel or vertical with the polarization direction of described light beam to be measured;

2. utilize described device for testing polarization to treat that photometry Shu Jinhang measures and after data processing, finally obtain the Stokes' parameter and the degree of polarization of described light beam to be measured.

When the polarization direction of the unknown light beam to be measured, its concrete measuring process is as follows:

1. utilize described device for testing polarization to measure and after data processing, obtain the Stokes' parameter and the polarization direction of the light beam to be measured first time of light beam to be measured by existing method;

2. the light transmission shaft direction of adjusting described analyzer is parallel or vertical with the polarization direction of described light beam to be measured;

3. utilize described device for testing polarization to treat that photometry Shu Jinhang measures for the second time and after data processing, finally obtain the Stokes' parameter and the degree of polarization of described light beam to be measured.

Described phase delay device is for producing quarter-wave plate, electrooptic modulator or the light ball modulator of 90 ° of phase delays.

The described phase delay device system for winding of described driver drives optical axis at the uniform velocity rotates, perhaps by driving the position of at least four different angles between fast axle that the phase delay device rotation can be provided with phase delay device and the described analyzer light transmission shaft.

Described photodetector is two-dimensional array detector or point probe.

Polarization position angle according to described light beam to be measured, the light transmission shaft direction of adjusting described analyzer is parallel or vertical with the polarization direction of described light beam to be measured, can effectively reduce the influence of the angle orientation error of each device in the foozle, measuring process of phase delay device and analyzer to measurement result.

The present invention has been owing to adopted technique scheme, compares with technology formerly, has the following advantages and good effect:

1, because in the desirable phase delay device of deep ultraviolet wave band manufacturing property and analyzer difficulty, the error between actual parameter such as the light transmission shaft direction of the retardation of phase delay device, quick shaft direction and analyzer, extinction ratio and the design parameter is with the measuring accuracy of polarisation-affecting degree.When utilizing light beam polarization pick-up unit of the present invention to measure, place and the perpendicular or parallel direction of light beam polarization direction to be measured, can effectively reduce the influence that above-mentioned foozle is measured degree of polarization by light transmission shaft with analyzer.

2, measure in the process of light beam Stokes' parameter to be measured at the rotatable phase delay device, there are positioning error in the initial fast shaft angle degree of phase delay device, the light transmission shaft angle of analyzer, measuring accuracy with the polarisation-affecting degree, place and the parallel or vertical direction of light beam polarization direction to be measured by the light transmission shaft that will adjust analyzer, can effectively reduce the influence that above-mentioned positioning error is measured degree of polarization.

Description of drawings

Fig. 1 is the employed device for testing polarization synoptic diagram of method of raising light beam polarization degree measuring accuracy of the present invention.

Fig. 2 is the synoptic diagram of illumination iris polarization parameter pick-up unit in the existing projection aligner.

Embodiment

Below in conjunction with embodiment and accompanying drawing the present invention is further specified, but should not limit protection scope of the present invention with this.

The present invention improve light beam polarization degree measuring accuracy the employed device for testing polarization of method structural representation as shown in Figure 1.As shown in Figure 1, device for testing polarization used in the present invention comprises phase delay device 2, analyzer 3 and the photodetector 4 that sets gradually along the apparatus system optical axis, the output of this photodetector 4 connects signal processing system 5, but described phase delay device 2 is the rotation of winding apparatus systematic optical axis under the driving of driver 6, light beam 1 to be measured is parallel to systematic optical axis and is incident to described phase delay device 2 and analyzer 3, and by described photodetector 4 detections, the electric signal of these photodetector 4 outputs is sent into described signal processing system 5 and is carried out data processing.

It is as follows that the present invention improves the concrete measuring process of method (present embodiment is the polarization direction of unknown light beam to be measured 1) of light beam polarization degree measuring accuracy:

1. utilize described device for testing polarization to measure and after data processing, obtain the Stokes' parameter and the polarization direction of light beam to be measured 1 first time of light beam 1 to be measured by existing method;

2. the light transmission shaft direction of adjusting described analyzer 3 is parallel or vertical with the polarization direction of described light beam 1 to be measured;

3. utilizing described device for testing polarization to treat photometry bundle 1 carries out measuring the second time and after data processing, finally obtaining the Stokes' parameter and the degree of polarization of described light beam to be measured 1.

Described phase delay device 2 is for producing quarter-wave plate, electrooptic modulator or the light ball modulator of 90 ° of phase delays.Phase delay device 2 is a quarter-wave plate in the present embodiment.

Described driver 6 can drive phase delay device 2 system for winding optical axises and at the uniform velocity rotate, and perhaps can be arranged to the fast axle of few four different phase delay device 2 and the angle between analyzer 3 light transmission shafts by driving phase delay device 2 rotations.Driver 6 can drive phase delay device 2 system for winding optical axises and at the uniform velocity rotates in the present embodiment.

Described analyzer 3 is 100% for the transmitance of the linearly polarized light of specific direction in the ideal case, and this direction is the light transmission shaft direction of analyzer 3; And the transmitance of the linearly polarized light vertical with this specific direction is 0.Definition is parallel to the light transmission shaft direction and is extinction coefficient p perpendicular to the ratio of the axial linear polarization light intensity of printing opacity transmitance, and ideally p be an infinity.Analyzer 3 is a polarizing prism in the present embodiment.

The foozle of described phase delay device 2 and analyzer 3 comprises phase-delay quantity error, the light transmission shaft deflection error of quick shaft direction sum of errors analyzer 3, the extinction ratio error of phase delay device 2; The angle orientation error of phase delay device 2 and analyzer 3 comprises the initial quick shaft direction positioning error of phase delay device 2 and the light transmission shaft direction positioning error of analyzer 3 in the described measuring process.

Described photodetector 4 is two-dimensional array detector or point probe.Photodetector 4 is two-dimensional array CCD in the present embodiment, with the degree of polarization distribution of measuring beam.

Described signal processing system 5 utilize technology 1 formerly and formerly the data processing method in the technology 2 electric signal of photodetector output is handled, obtain the Stokes' parameter and the degree of polarization of light beam 1 to be measured.

Xyz coordinate system shown in definition Fig. 1, wherein the z axle is a deflection detection apparatus systematic optical axis direction, the xy plane is the plane vertical with systematic optical axis.If the Stokes vector of light beam 1 to be measured is S=[S ₀, S ₁, S ₂, S ₃] ^T(upper right corner " T " representing matrix transposition), its degree of polarization is:

$V=\sqrt{\frac{S_1^2+{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">S</figure-callout>}}_2^2+{\mathrm{<figure-callout\; id="3"\; label="S"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">S</figure-callout>}}_3^2}{S_0^2}}.---\left(1\right)$

For linearly polarized light, degree of polarization V is the important parameter that characterizes the polarization characteristic of this linearly polarized light.

Angle between definition wires polarized light polarization direction and the x axle positive dirction is the polarization position angle

Its scope is

Angle between definition quarter-wave plate fast axis and the x axle positive dirction is fast shaft angle degree θ, and its scope is-90 °≤θ≤90 °; Angle between definition polarizing prism light transmission shaft and the x axle positive dirction is the light transmission shaft angle [alpha], and its scope is-90 °≤α≤90 °.

The Muller matrix of the quarter-wave plate of described systematic optical axis rotation around device for testing polarization is:

$M\left(\mathrm{\&theta;}\right)=\left[\begin{array}{cccc}1,& 0,& 0,& 0\\ 0,& {\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}}^{2}2\mathrm{\&theta;}+{\sin }^{2}2\mathrm{\&theta;}\cos \mathrm{\&delta;},& \sin 2\mathrm{\&theta;}\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&theta;}-\sin 2\mathrm{\&theta;}\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&theta;}\cos \mathrm{\&delta;},& -\sin 2\mathrm{\&theta;}\sin \mathrm{\&delta;}\\ 0,& \sin 2\mathrm{\&theta;}\cos 2\mathrm{\&theta;}-\sin 2\mathrm{\&theta;}\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&theta;}\cos \mathrm{\&delta;},& {\sin }^{2}2\mathrm{\&theta;}+{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}}^{2}2\mathrm{\&theta;}\cos \mathrm{\&delta;},& \cos 2\mathrm{\&theta;}\sin \mathrm{\&delta;}\\ 0,& \sin 2\mathrm{\&theta;}\sin \mathrm{\&delta;},& -\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&theta;}\sin \mathrm{\&delta;},& \cos \mathrm{\&delta;}\end{array}\right],---\left(2\right)$

Wherein, δ is the phase-delay quantity of quarter-wave plate, ideally δ=pi/2.

The light transmission shaft angle is that the Muller matrix of the polarizing prism of α is:

$P\left(\mathrm{\&alpha;}\right)=\left[\begin{array}{cccc}1,& \frac{p-1}{p+1}\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&alpha;},& \frac{p-1}{p+1}\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">sin</figure-callout>}2\mathrm{\&alpha;},& 0\\ \frac{p-1}{p+1}\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&alpha;},& {\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}}^{2}2\mathrm{\&alpha;}+\frac{2\sqrt{p}}{p+1}{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">sin</figure-callout>}}^{2}2\mathrm{\&alpha;},& \mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">sin</figure-callout>}2\mathrm{\&alpha;}\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&alpha;}-\frac{2\sqrt{p}}{p+1}\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">sin</figure-callout>}2\mathrm{\&alpha;}\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&alpha;},& 0\\ \frac{p-1}{p+1}\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">sin</figure-callout>}2\mathrm{\&alpha;},& \sin 2\mathrm{\&alpha;}\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&alpha;}-\frac{2\sqrt{p}}{p+1}\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">sin</figure-callout>}2\mathrm{\&alpha;}\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&alpha;},& {\sin }^{2}2\mathrm{\&alpha;}+\frac{2\sqrt{p}}{p+1}{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}}^{2}2\mathrm{\&alpha;},& 0\\ 0,& 0,& 0,& \frac{2\sqrt{p}}{p+1}\end{array}\right].---\left(3\right)$

Behind light beam 1 process quarter-wave plate to be measured and the polarizing prism, Stokes vector is S '=P (α) M (θ) S.Because the total intensity of the first line display light wave of Stokes vector, the light intensity that photodetector 4 can detect i.e. intensity level for this reason, so only be concerned about the first line number value of Stokes vector herein.Photodetector 4 is an area array CCD in the present embodiment, and its each pixel all obtains the relevant data of light intensity, the data of each pixel is handled the Stokes' parameter that obtains this pixel place light beam 1 to be measured.For the ease of understanding, existing is that example describes with a pixel.

In the ideal case, promptly=when pi/2, p are infinitely great, have:

S ₀′(θ)＝S ₀+S ₁[cos2αcos ²2θ+sin2αsin2θcos2θ]， (4)

+S ₂[cos2αsin2θcos2θ+sin2αsin ²2θ]+S ₃(sin2αcos2θ-cos2αsin2θ)

During measurement, rotate quarter-wave plate and change θ.With S ₀' as the function of θ, and it is carried out fourier expansion:

${S_0}^{\&prime;}\left(\mathrm{\&theta;}\right)=\frac{a_0}{2}+\underset{n}{\mathrm{\&Sigma;}}(a_n\cos \mathrm{n\&theta;}+b_n\sin \mathrm{n\&theta;}),---\left(5\right)$

For by S ₀' (θ) obtain coefficient a _nAnd b _n, can use following formula:

$a_n=\frac{1}{\mathrm{\&pi;}}\underset{-\mathrm{\&pi;}}{\overset{\mathrm{\&pi;}}{\&Integral;}}{S_0}^{\&prime;}\left(\mathrm{\&theta;}\right)\cos \mathrm{n\&theta;d\&theta;},---\left(6\right)$

$b_n=\frac{1}{\mathrm{\&pi;}}\underset{-\mathrm{\&pi;}}{\overset{\mathrm{\&pi;}}{\&Integral;}}{S_0}^{\&prime;}\left(\mathrm{\&theta;}\right)\sin \mathrm{n\&theta;d\&theta;}.---\left(7\right)$

Obtain a shown in following formula (8)-(12) so respectively ₀, a ₂, b ₂, a ₄And b ₄:

$\frac{a_0}{2}=S_0+\frac{p-1}{2(p+1)}(S_1\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&alpha;}+{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">S</figure-callout>}}_2\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">sin</figure-callout>}2\mathrm{\&alpha;}),---\left(8\right)$

$a_2=\frac{p-1}{p+1}{\mathrm{<figure-callout\; id="3"\; label="S"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">S</figure-callout>}}_3\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">sin</figure-callout>}2\mathrm{\&alpha;},---\left(9\right)$

${\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">b</figure-callout>}}_2=-\frac{p-1}{p+1}{\mathrm{<figure-callout\; id="3"\; label="S"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">S</figure-callout>}}_3\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&alpha;},---\left(10\right)$

$a_4=\frac{p-1}{2(p+1)}(S_1\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&alpha;}-{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">S</figure-callout>}}_2\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">sin</figure-callout>}2\mathrm{\&alpha;}),---\left(11\right)$

$b_4=\frac{p-1}{2(p+1)}(S_1\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">sin</figure-callout>}2\mathrm{\&alpha;}+{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">S</figure-callout>}}_2\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&alpha;}).---\left(12\right)$

The a that utilization obtains ₀, a ₂, b ₂, a ₄And b ₄, can calculate 4 the Stokes' parameter Ss corresponding with the polarization state of light beam 1 to be measured ₀, S ₁, S ₂, S ₃:

$S_0=\frac{a_0}{2}-(a_4\cos 4\mathrm{\&alpha;}+b_4\sin 4\mathrm{\&alpha;}),---\left(13\right)$

$S_1=\frac{2(p+1)}{(p-1)}(a_4\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&alpha;}+b_4\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">sin</figure-callout>}2\mathrm{\&alpha;}),---\left(14\right)$

${\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">S</figure-callout>}}_2=\frac{2(p+1)}{(p-1)}(b_4\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&alpha;}+a_4\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">sin</figure-callout>}2\mathrm{\&alpha;}),---\left(15\right)$

${\mathrm{<figure-callout\; id="3"\; label="S"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">S</figure-callout>}}_3=\frac{-(p+1)b_2}{(p-1)\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&alpha;}}=\frac{(p+1)a_2}{(p-1)\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">sin</figure-callout>}2\mathrm{\&alpha;}}.---\left(16\right)$

But when actual measurement owing in device manufacturing and measuring process, may have various errors, as the fast shaft angle degree error of quarter-wave plate, phase-delay quantity sum of errors polarizing prism light transmission shaft angular error, extinction ratio error etc., obtain this moment about S ₀, S ₁, S ₂, S ₃Quaternary linear function group be:

${S_0}^{\&prime;}\left(\mathrm{\&theta;}\right)=$

$S_0+S_1\frac{p-1}{p+1}\{\cos 2(\mathrm{\&alpha;}+\mathrm{\&Delta;\&alpha;})+[{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}}^{2}2(\mathrm{\&theta;}+\mathrm{\&Delta;\&theta;})+{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">sin</figure-callout>}}^{2}2(\mathrm{\&theta;}+\mathrm{\&Delta;\&theta;})\cos \mathrm{\&delta;}]+\sin 2(\mathrm{\&alpha;}+\mathrm{\&Delta;\&alpha;})\sin 2(\mathrm{\&theta;}+\mathrm{\&Delta;\&theta;})\cos 2(\mathrm{\&theta;}+\mathrm{\&Delta;\&theta;})(1-\cos \mathrm{\&delta;})\}$

$+S_2\frac{p-1}{p+1}\{\cos 2(\mathrm{\&alpha;}+\mathrm{\&Delta;\&alpha;})\sin 2(\mathrm{\&theta;}+\mathrm{\&Delta;\&theta;})\cos 2(\mathrm{\&theta;}+\mathrm{\&Delta;\&theta;})(1-\cos \mathrm{\&delta;})+\sin 2(\mathrm{\&alpha;}+\mathrm{\&Delta;\&alpha;})[{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">sin</figure-callout>}}^{2}2(\mathrm{\&theta;}+\mathrm{\&Delta;\&theta;})+{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000238576300012.png"\; state="\{\{state\}\}">cos</figure-callout>}}^{2}2(\mathrm{\&theta;}+\mathrm{\&Delta;\&theta;})\cos \mathrm{\&delta;}\left]\right\}$

$+S_3\frac{p-1}{p+1}[\sin 2(\mathrm{\&alpha;}+\mathrm{\&Delta;\&alpha;})\cos 2(\mathrm{\&theta;}+\mathrm{\&Delta;\&theta;})-\cos 2(\mathrm{\&alpha;}+\mathrm{\&Delta;\&alpha;})\sin 2(\mathrm{\&theta;}+\mathrm{\&Delta;\&theta;})]\sin \mathrm{\&delta;},---\left(17\right)$

Wherein: Δ α is the angular error of polarizing prism light transmission shaft, and Δ θ is initial (being the original state of quarter-wave plate when not rotating) fast shaft angle degree error of quarter-wave plate.

When having above-mentioned error, the pixel actual detection of CCD to light intensity represent by (17) formula, and calculate Stokes' parameter S ₀, S ₁, S ₂, S ₃The time light intensity used be (4) formula, thereby there is error in the Stokes' parameter that causes obtaining, the result of calculation of polarisation-affecting degree V.

Our emulation under different error conditions the error of degree of polarization V.

For linearly polarized light, when there was error delta θ=1 ° in the fast shaft angle degree θ of quarter-wave plate, the error delta V of degree of polarization V was with the light transmission shaft angle [alpha] of polarizing prism and the polarization position angle of light beam to be measured 1

Variation as shown in table 1.As shown in Table 1, when the light transmission shaft angle [alpha] of polarizing prism and the polarization position angle of light beam to be measured 1

Between satisfy

Or

(α≤0) or

When (α＞0), the error of degree of polarization V is 0.And the light transmission shaft direction of working as polarizing prism is parallel with the polarization direction of light beam 1 to be measured

Or vertical (

Or-90 °) time, the absolute value of the error of degree of polarization V is 0.001, can ignore.For linearly polarized light, when there was error delta α=1 ° in the light transmission shaft angle [alpha] of polarizing prism, the error delta V of degree of polarization V was with the light transmission shaft angle [alpha] of polarizing prism and the polarization position angle of light beam to be measured 1

Variation as shown in table 2.As shown in Table 2, when the light transmission shaft direction of polarizing prism parallel with the polarization direction of light beam 1 to be measured

Or vertical ( Or-90 °) time, the error of degree of polarization V is 0.

For degree of polarization is 1 linearly polarized light, and when there were 2 ° of errors in the phase-delay quantity δ of quarter-wave plate, the error delta V of degree of polarization V was with the light transmission shaft angle [alpha] of polarizing prism and the polarization position angle of light beam to be measured 1

Variation as shown in table 3.As shown in Table 3, when the light transmission shaft direction of polarizing prism vertical with the polarization direction of light beam 1 to be measured (

Or-90 °) time, the error of degree of polarization V is 0.

For degree of polarization is 1 linearly polarized light, if there is error p=10000 in the polarizing prism extinction ratio, the error of degree of polarization V does not change with the angle of the light transmission shaft of polarizing prism, is definite value-0.0002, can ignore.

Figure 2 shows that the synoptic diagram of illumination iris polarization parameter pick-up unit in the projection aligner that technology formerly 1 proposes.For the linearly polarized light that uses in the projection aligner, when there is error in the fast shaft angle degree of phase delay device 2, during the light transmission shaft direction of selection analyzer 3 parallel or vertical with the polarization direction of light beam 1 to be measured (or near parallel or approaching vertical), then the error of degree of polarization V is 0 (or near 0); When there was error in analyzer 3 light transmission shaft angles, during the light transmission shaft direction of selection analyzer 3 parallel or vertical with the polarization direction of light beam 1 to be measured (or near parallel or approaching vertical), the error of degree of polarization V was 0 (or near 0); When there was error in the phase-delay quantity of phase delay device 2, during the light transmission shaft direction of selection analyzer 3 vertical with the polarization direction of light beam 1 to be measured (or near vertical), the error of degree of polarization V was near 0; When there was error p=10000 in the extinction ratio of analyzer 3, the axial selection of the printing opacity of analyzer 3 is the result of polarisation-affecting degree V not, and the error of degree of polarization V is very little, can ignore.

By above result as can be known, when there are dissimilar error in phase delay device 2 and analyzer 3, polarization direction according to linearly polarized light in the illumination iris of projection aligner setting, select analyzer 3 light transmission shaft directions parallel or vertical with the polarization direction of setting (or near parallel or approaching vertical), the error of degree of polarization V equals or near 0, can effectively reduce the influence of the correlated error of device to the light beam polarization measurement result at this moment.When light beam to be measured 1 polarization direction is unknown, can be under the situation that analyzer 3 light transmission shaft directions are set arbitrarily, the polarization direction of rough measure light beam in advance, it is parallel or vertical with the polarization direction of measuring in advance to adjust the angle of analyzer 3 light transmission shafts according to measurement result again, then the error of degree of polarization V also can effectively reduce the influence of device error to measurement result near 0.

During table 1. Δ θ=1 °, Δ V is with the light transmission shaft angle [alpha] of polarizing prism 3 and the polarization position angle of light beam to be measured 1

Variation

During table 2. Δ α=1 °, Δ V is with the light transmission shaft angle [alpha] of polarizing prism 3 and the polarization position angle of light beam to be measured 1

Variation

When there were 2 ° of errors in table 3. δ, Δ V was with the light transmission shaft angle [alpha] of polarizing prism 3 and the polarization position angle of light beam to be measured 1

Variation

Claims (6)

1. method that improves light beam polarization degree measuring accuracy, the device for testing polarization that uses comprises the phase delay device that sets gradually along the apparatus system optical axis, analyzer and photodetector, the output of this photodetector connects signal processing system, but described phase delay device is the rotation of winding apparatus systematic optical axis under the driving of driver, parallel beam to be measured is incident to described phase delay device and analyzer in systematic optical axis, and by described photodetector detection, the electric signal of this photodetector output is sent into described signal processing system and is carried out data processing, it is characterized in that, polarization direction according to described light beam to be measured, adjust the light transmission shaft direction of described analyzer parallel with the polarization direction of described light beam to be measured or vertical after, carry out the measurement of light beam polarization degree to be measured again.

2. the method for raising light beam polarization degree measuring accuracy according to claim 1 is characterized in that: when generally knowing the polarization direction of light beam to be measured, its concrete measuring process is as follows:

1. the light transmission shaft direction of adjusting described analyzer is parallel or vertical with the polarization direction of described light beam to be measured;

2. utilize described device for testing polarization to treat that photometry Shu Jinhang measures and after data processing, finally obtain the Stokes' parameter and the degree of polarization of described light beam to be measured.

3. the method for raising light beam polarization degree measuring accuracy according to claim 1 is characterized in that: when the polarization direction of the unknown light beam to be measured, its concrete measuring process is as follows:

1. utilize described device for testing polarization to measure and after data processing, obtain the Stokes' parameter and the polarization direction of the light beam to be measured first time of light beam to be measured by existing method;

2. the light transmission shaft direction of adjusting described analyzer is parallel or vertical with the polarization direction of described light beam to be measured;

3. utilize described device for testing polarization to treat that photometry Shu Jinhang measures for the second time and after data processing, finally obtain the Stokes' parameter and the degree of polarization of described light beam to be measured.

4. the method for raising light beam polarization degree measuring accuracy according to claim 1 is characterized in that described phase delay device is for producing quarter-wave plate, electrooptic modulator or the light ball modulator of 90 ° of phase delays.

5. the method for raising light beam polarization degree measuring accuracy according to claim 1, it is characterized in that the described phase delay device system for winding of described driver drives optical axis at the uniform velocity rotates, perhaps by driving the position of at least four different angles between fast axle that the phase delay device rotation can be provided with phase delay device and the described analyzer light transmission shaft.

6. the method for raising light beam polarization degree measuring accuracy according to claim 1 is characterized in that described photodetector is two-dimensional array detector or point probe.

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