JP5308639B2 - Method and system for defect detection - Google Patents

Description

Related applications

  [0001] This application claims priority to US Provisional Patent Application No. 60 / 821,056, filed August 1, 2006.

Field of Invention

  [0002] The present invention relates generally to the field of reticle inspection, particularly reticle evaluation with aerial image emulating optics.

Background of the Invention

  [0003] Modern microelectronic devices are typically created using a photolithographic process. In this process, a semiconductor wafer is first coated with a layer of photoresist. This photoresist layer is then developed after exposure (during the so-called exposure process) to irradiation light using a reticle (also called a photomask or mask). During development, the exposed positive photoresist is removed (alternatively, the unexposed negative photoresist is removed) and the remaining photoresist creates an image of the reticle on the wafer. Thereafter, the top layer of the wafer is etched. Thereafter, the remaining photoresist is stripped. In the case of multiple layer wafers, the above procedure is then repeated to create a later patterned layer.

  [0004] Those skilled in the art should recognize that in order to create a semiconductor product that can be used at any time, the reticle should be as defect-free as possible, preferably completely defect-free. Therefore, a reticle evaluation tool is needed to detect various defects in the reticle that can reduce the manufacturing yield of microelectronic circuits.

  [0005] It is customary to correlate the electric field immediately behind the mask (reticle) with the electric field of the impinging light due to the mask function. The concept of masking is also useful for imaging and projection in which the coherent light is partially applied, where imaging is typically described by several variations of the Hopkins equation. For masks with pattern elements that are large compared to the irradiation wavelength, Kirchoff's also known as “thin film mask approximation” to calculate the resulting aerial image, or alternatively, the intensity pattern on the wafer Boundary conditions can be used without hindrance. However, as with modern masks, once the member on the mask is as large as the illumination wavelength, this approximation is no longer valid and the transmission of the mask is Depending on the polarization state and angle.

  [0006] For some members common to modern reticles, typically for members with a high degree of spatial symmetry, the amplitude, phase and polarization state of the diffracted light can be determined, for example, by analytical results or useful Prediction can be based on a numerical model. In the case of other reticle patterns where such calculations are very inefficient or too complex, certain interferometry or to obtain a sufficient approximation of the characteristics of the diffraction orders that carry most of the image output Along with wavefront sensing, knowledge of reticle design can be used.

  [0007] Rapid downsizing of semiconductor product feature dimensions has resulted in an increase in numerical aperture in exposure systems such as steppers. Currently, the numerical aperture of the exposure system is increasing beyond 1.4 to 1.4 and is expected to reach 1.8 in the near future.

  [0008] At high numerical aperture values representing large angles of incidence, the exposure process is susceptible to effects associated with polarization, particularly high angle, incident light on the resist.

  [0009] Spatial imaging tools, such as a spatial inspection tool, a spatial inspection tool, try to mimic the exposure process and apply an imaging process different from the exposure process. During the exposure process, the image of the reticle is reduced and during the imaging process, the image of the reticle is enlarged. This expansion results in a decrease in the angle of incidence with the same expansion factor that can be on the order of several hundred. The result of this magnification process is that the polarization effect that occurs on the wafer surface is not emulated by the spatial imaging system. In particular, the exposure process substantially reduces the contrast ratio of p-polarized light (also referred to as TM) to the contrast ratio of s-polarized light (also referred to as TE), while the imaging process performs such a reduction. Absent.

  [00010] FIGS. 1 and 2 illustrate the difference between a p-polarized component and an s-polarized component.

  [00011] FIG. 1 illustrates an exposure system 10 that includes a light source 12 that provides s-polarized light. Diffraction creates two or more coherent rays (such as rays 15a and 15b in FIG. 1) that appear at different locations on the pupil plane, each of which is in an image plane from a different direction. To reach.

  [00012] When these coherent rays strike the wafer from different directions, all field vectors combine in a vector superposition to create a point electric field.

  [00013] The aerial image is the intensity of this electric field. The angular difference between the two incident beams creates a high angle polarization effect.

  [00014] The light source 12 is behind the reticle 14 and the objective lens 16. The s-polarized light travels through the transparent portion of the reticle 14 toward the objective lens 16 that projects the image of the reticle 14 onto the wafer 20. The electric field vector of s-polarized light is perpendicular to the plane of FIG. Drawer 30 is a plan view of the electric field vector of s-polarized radiation at the pupil plane or at the top of objective lens 16, while drawer 32 is a side view of coherent rays 42 and 44 in the wafer (or image) plane. . Two points 46 and 48 represent the direction of the electric field vector of these rays.

  [00015] FIG. 2 illustrates the same exposure system 10, but the light source 12 provides p-polarized light. The intensity vector of the p-polarized light appears in the plane of FIG. Drawer 34 is a plan view of the electric field vector of p-polarized radiation at the top of objective lens 16, while drawer 36 is a side view of coherent rays 52 and 54 on the wafer surface. Two points 56 and 58 represent the electric field vectors associated with these rays. Note that all illumination sources can be described as generating radiation that includes both S and P polarization components.

  [00016] The aerial image is the squared self-dot product of the electric field vector of light impinging on the wafer or sensor. The electric field can be divided into two independent polarization components, a p-polarization (TM) component and an s-polarization (TE) component. The theory of imaging at high numerical apertures indicates that due to the large angle of incidence experienced in high numerical aperture projections, the sum of s-polarized vectors differs significantly from the sum of p-polarized vectors. In practice, the angle between the electric field vectors of two s-polarized beams that are focused on the image plane from different directions is independent of the polarization angle (the angle between the beam and the optical axis of the system), This is not the case for these two p-polarized cases. This implies a strong dependence of the contrast of the image formed at the angle of incidence on the image plane by p-polarized light. When the typical feature size on the photomask is reduced, the light focused at a high incident angle is output at the spatial frequency required for good imaging due to the critical dependence on the beam at the extreme incident angle. Convey a significant proportion of

  [00017] Also, for NA values above 0.7, both modalities are derived from the properties obtained with low numerical aperture imaging, thanks to the increased relative power delivered by the focused beam at high incidence angles. Generate images that can be significantly separated.

  [00018] Projection systems typically utilize very high angles of incidence, but the large magnification applied by the imaging process results in light that is focused on the image plane with a fairly small angle of incidence. This fundamental difference results in different images created by the same mask pattern, respectively, on the wafer and the image plane of the imaging system.

  [00019] These differences between the exposure process and the imaging process should be corrected to allow the imaging system to mimic the exposure process in a reliable manner.

  [00020] Accordingly, there is a need to provide an effective system and method for reticle evaluation.

Summary of the Invention

  [00021] A method for reticle evaluation comprises: (i) obtaining a plurality of images of a reticle under different polarization conditions during an imaging process; and (ii) (i) the plurality of images and (ii) the Generating an output aerial image in response to a difference between an imaging process and an exposure process, during which the image of the reticle is projected onto a wafer.

  [00022] A computer readable medium having embodied therein a computer readable code for reticle evaluation, wherein the computer readable code obtains multiple images of the reticle under different polarization conditions during an imaging process. Instructions for generating an output aerial image in response to (i) the plurality of images and (ii) a difference between the imaging process and the exposure process, during the exposure process, A computer readable medium on which an image of a reticle is projected onto a wafer.

  [00023] A system for reticle evaluation includes a storage device adapted to store information representative of a plurality of images of a reticle and a processor coupled to the storage device, the processor being configured during an imaging process. Receiving information representative of the plurality of images acquired under different polarization conditions, and generating an output aerial image according to (ii) the plurality of images and (ii) a difference between the imaging process and the exposure process. The image of the reticle is projected onto the wafer during the exposure process.

  [00024] A method for spatial imaging is to control the intensity and polarization of a plurality of rays during an imaging process to define a reticle illumination condition that is substantially equal to the illumination condition of the reticle during an exposure process. The image of the reticle including being projected onto a wafer during the exposure process and acquiring the image of the reticle.

  [00025] A system applies an imaging process and controls the intensity and polarization of a plurality of rays during the imaging process to define a reticle illumination condition that is substantially equal to the illumination condition of the reticle during an exposure process. An imaging optics adapted to the imaging optics, wherein the image of the reticle is projected onto a wafer during the exposure process, and a sensor adapted to acquire the image of the reticle Including.

Detailed Description of Exemplary Embodiments

  [00026] The embodiments will now be described, by way of non-limiting examples only, with reference to the accompanying drawings in order to understand the present invention and to understand how it can actually be implemented. explain.

  [00031] The term "reticle" can be interpreted according to the meaning of a reticle or mask, along with its conventional meaning. A reticle generally includes a transparent substrate on which a layer of opaque material (such as chromium) is formed. The reticle may also include one or more additional materials formed under the opaque material, such as a reticle, an adhesive layer, an antireflection layer, a phase shift layer, an attenuation layer, and the like. Typical reticles include binary reticles, reticles that include optical proximity correction members, phase-shift masks (PSMs), ternary attenuated PSMs, alternate PSMs, attenuated PSMs, halftone PSMs, clear field reticles and dark Includes field reticle.

  [00032] The term "exposure system" as used herein generally refers to any lithography system that uses electromagnetic radiation to print an image of a reticle onto a sample. The exposure system may include a stepper, a scanning projection system or a step and repeat system. An exposure process is a lithography process applied by the exposure system.

  [00033] The term "imaging system" as used herein generally refers to a system that generates an image of a reticle. The imaging system may be a reticle evaluation system such as a reticle inspection system, a reticle inspection system, or a reticle measurement system. The imaging system applies an imaging process.

  [00034] Note that all figures are not to scale.

  [00035] Systems, methods, and computer program products for reticle evaluation are provided.

  [00036] The system, method, and computer program product correct for differences between the exposure process and imaging by receiving or acquiring at least one image, and if multiple images are acquired, then each Images are acquired under different polarization conditions, and optionally under different phase (interference) conditions. The difference between the polarization (and optionally phase) conditions is to separate the TM and TE components of the aerial image and apply a correction transformation to the TM and TE images to produce an output aerial image. It makes it possible to add corrected TEs and TMs with appropriate weights.

  [00037] Note that one aerial image can be obtained while removing the TM component and the other aerial image can be obtained while removing the TE component, but this is not necessarily so. To do. For example, at least one aerial image can include both components. Assuming that different polarization (and optionally phase) states are known, the TE and TM components can be extracted.

  [00038] These images can be obtained by using one or more polarization components in the illumination channel and / or in the collection channel.

  [00039] Conveniently, the collection channel includes a polarizing (and optionally phase) filter at the aperture plane. The details of these (one or more) polarization (and optionally phase) filters depend on several illumination conditions and the pattern on the mask.

  [00040] Note that to simplify the description, the following description refers primarily to polarization. Note that, according to various embodiments of the present invention, the systems and methods can also accommodate phase differences. Thus, the phase retarder, phase shifter, and phase effector can also be used using a phase response spatial imaging process that can correct for phase related differences between the imaging and exposure processes.

  [00041] Conveniently, both the collection channel and the illumination channel include a polarizing filter.

  [00042] Once the TM and TE components of the aerial image are measured, they undergo a correction process. The correction process includes decomposing the TE and TM components of the aerial image into their spatial spectral components. The decomposition can include applying a Fourier transform. After one or more spectral components are corrected using a correction function, a weighted inverse function is applied to provide a corrected polarization component of the aerial image. The corrected TE and TM components are then summed to provide a so-called output aerial image.

  [00043] FIG. 3 illustrates an imaging system 80 according to an embodiment of the invention.

  [00044] According to an embodiment of the present invention, an imaging system 80 is provided. The imaging system 80 includes an illumination channel 81 and a collection channel 91. The illumination channel 81 includes a light source 82 and a condenser lens 87. The condensing channel 91 includes an objective lens 92 and a camera 93.

  [00045] According to an embodiment of the invention, the illumination channel 82 also includes a polarizer 83. Note that the phase retrieval method also requires splitting the illumination channel into several subchannels (corresponding to several beams).

  [00046] For ease of explanation, FIG. 3 illustrates a single polarizer 83 and a single camera 93 belonging to the illumination path.

  [00047] Conveniently, the mask 14 is disposed on the object plane 89 and the polarizer 83 is disposed on the illumination pupil plane 95. The reticle 14 and the polarizer 83 are arranged away from the condenser lens 87 by a focal length.

  [00048] Note that additionally or alternatively, the collection channel 91 can include one or more polarizers. Note that knowledge of the relative phase between coherent beams incident on the image plane from different directions may require some interferometry, so the system can include phase filters, phase plates, etc. .

  [00049] According to embodiments of the present invention, the polarizer 83 can control the intensity and polarization of light at the illumination pupil plane 95. Thus, the polarizer actually controls the polarization and intensity of rays of different incident angles. In particular, polarization and attenuation can be measured across the pupil plane.

  [00050] Conveniently, the polarization and intensity of multiple locations across the illumination pupil plane can be controlled.

  [00051] Furthermore, the collection channel 91 can include a belt run lens in front of the camera so that the acquired image is an image of the pupil plane (also known as a belt run image). To do.

  [00052] Furthermore, it is noted that the collection channel 91 can include multiple cameras that can simultaneously acquire multiple aerial images.

  [00053] According to embodiments of the present invention, the cameras acquire different images depending on their focus conditions. For example, one camera can acquire a focus image and the other camera can acquire an out-of-focus image.

  [00054] According to another embodiment of the present invention, the camera can acquire different images depending on their polarization conditions. One camera can acquire an image projected with a particular polarization, and the other camera can acquire an image projected with another polarization.

  [00055] Those skilled in the art will appreciate that different combinations of focus and polarization conditions can be provided to the imaging system.

  [00056] The camera 93 sends information representing the acquired image to the storage device 95. The storage device 95 is connected to the processor 96. The processor 96 is connected to the storage device 95 and receives (i) information representing a plurality of images acquired under different polarization conditions, (ii) an aerial image (or image set), and an exposure process. And is adapted to produce an output aerial image corresponding to the plurality of images during which the image of the reticle is projected onto the wafer.

  [00057] The processor 95 may also analyze the aerial image, as further illustrated in FIG. This analysis includes die-to-die comparisons, die-to-database comparisons, determining process windows, evaluating reticle member critical dimensions, and the critical dimensions of parts printed by the exposure process. It can include evaluating, determining the printing suitability of a defect on the reticle, generating a defect map, generating a trace map, performing a statistical analysis of the defect or member, and the like.

  [00058] The imaging system 80 also includes a display 99 that displays an output aerial image and information representing an analysis of the output aerial image. For example, the display 99 can be used to display a map of possible defects that can be displayed.

  [00059] According to another embodiment of the invention, processing of the image is performed by a remote processor that receives information representing the plurality of images (obtained under different polarization conditions) and performs the functions described above. Is done.

  [00060] FIG. 4 illustrates a method 100 for reticle evaluation, according to an embodiment of the invention.

  [00061] The method 100 begins at stage 110 where multiple images of the reticle are obtained under different polarization (and optionally phase) conditions during the imaging process. This can be achieved by using one or more polarization components and optionally one or more phase elements and retarders. Furthermore, note that the resulting image may be a belt run image. Further, note that the obtained image may be an image acquired at a different location.

  [00062] Stage 110 utilizes a plurality of detection channels, each of which is characterized by: (i) each characterized by a different polarization (and optionally phase) identification; (ii) an illumination channel Obtaining a plurality of images while changing the polarization characteristics (and the optical path difference if necessary), (iii) changing the polarization characteristics and, if necessary, the optical paths of the detection channel and the illumination channel At least one of these or a combination thereof.

  [00063] Stage 110 is followed by stage 120 that generates an output aerial image corresponding to the plurality of images and corresponding to the difference between the imaging process and the exposure process. During the exposure process, an image of the reticle is projected onto the wafer.

  [00064] Conveniently, stage 120 may include correcting for these differences.

  [00065] Note that the conversion between the exposure process and the imaging process can be calculated and stored for later use in processing one or more other images.

  [00066] According to an embodiment of the invention, stage 120 includes generating an output aerial image corresponding to the polarization and optionally phase dependent characteristics of the exposure and imaging processes. Conveniently, the exposure and imaging processes react differently to p-polarized light and s-polarized light. Specifically, the exposure process results in an intensity pattern on the wafer, the pattern generally having a different contrast than the image created by the imaging system, and further being highly resistant to the polarization state of light. Dependent. The generation of the output aerial image should take this difference into account.

  [00067] Conveniently, stage 120 includes sub-stages 121-129.

  [00068] Stage 121 includes processing the plurality of images to provide different polarization components of the intermediate image. After undergoing the correction process, the intermediate image becomes an output aerial image. The intermediate image represents the result of the uncorrected imaging process, while the output aerial image will mimic the result of the exposure process.

  [00069] Stage 121 is followed by stage 123 that decomposes a particular polarization component of the intermediate image into its spatial spectral components.

  [00070] Stage 123 involves applying a Fourier transform, but other decomposition functions can be applied.

  [00071] Stage 123 is followed by stage 125 that applies a correction function to at least one of these spectral components.

  [00072] Stage 125 includes applying a correction function corresponding to at least one polarization dependent property. The stage also includes: (i) applying the correction function to a single spectral component; (ii) correcting the single spectral component corresponding to the pitch of the repetitive pattern of the reticle. Applying a function, (iii) applying a correction function inversely proportional to the square of the spectral frequency of the spectral component to the spectral component, and (iv) applying a correction function corresponding to the angle between incident lines. At least one or a combination thereof may also be included.

  [00073] FIG. 5 illustrates the relationship between the spectral components 201-204 of the s-polarized component of the intermediate image and the attenuation of these spectral components according to an embodiment of the present invention.

  [00074] The frequency of the spectral component 201 corresponds to the pitch of the repetitive pattern of the reticle. Other spectral components correspond to the product of this pitch.

  [00075] The horizontal curve 220 illustrates the response of the imaging system to s-polarized light, and the curve 222 illustrates the response of the exposure system to s-polarized light. The difference between these curves indicates the attenuation of these spectral components. This attenuation is typically inversely proportional to the square of these frequencies. Since the first spectral component 201 is relatively distant from the other spectral components, the first spectral component 201 attenuates dramatically with respect to the other spectral components.

  [00076] To simplify the correction process and allow for real-time or near real-time correction, the correction process can be focused on the first spectral component.

  [00077] Conveniently, each spectral component of the resolved image represents the result of two (or more) different coherent field interferences approaching from different directions separated by a particular angle of incidence. The result of this interference is proportional to the square of the vector sum of the interfering electric field. This relationship can be derived from the design scheme of the imaging system. Under the specific conditions that exist in new generation exposure systems, it has been found that each spectral component goes through a linear process of contrast change that depends on the angle between the incident lines and their polarization state. This is accompanied by a slight change in the spectral power conveyed by the different spectral components, i.e. a process that is particularly prone to high frequency spectral components. Simple wafer resist models and optical modeling can be used to derive and calibrate this linear relationship. After applying this linear correction transform to Fourier space, the weighted vector sum of all frequency components is inverted to receive the predicted image of the TE and TM polarization components.

  [00078] Referring back to FIG. 4, stage 125 is followed by stage 127 that reconstructs a particular polarization component of the intermediate image to provide a corrected polarization component of the intermediate image.

  [00079] After stage 127, an output aerial image corresponding to the corrected polarization component of the intermediate image, and advantageously corresponding to another polarization component of the intermediate image that is not subjected to the correction process. A generation stage 129 follows. Note that in most cases both polarization components of the intermediate image can undergo a correction process. Conveniently, stage 129 includes summing the polarization components of the intermediate image.

  [00080] Stage 120 may be followed by stage 130 for analyzing the output aerial image. The analysis includes the following: (i) estimating a critical dimension of a member of a wafer manufactured by an exposure process, (ii) estimating a critical dimension of a reticle member, (iii) the exposure process And (iv) measuring at least one of the out-of-focus polarization characteristics of the imaging process, or a combination thereof, corresponding to the focus measurement.

  [00081] Each of the various methods described above can be performed by a computer executing a computer program stored on a computer-readable medium. Accordingly, a computer readable medium is provided. The computer-readable medium has computer-readable code embodied therein for reticle evaluation, the computer-readable code having instructions for obtaining a plurality of images of the reticle under different polarization conditions; Generate an output aerial image corresponding to and between the exposure process in which the image of the reticle is projected onto the wafer and the imaging process in which the plurality of images are obtained in between. Instructions to do.

  [00082] Conveniently, the computer readable code comprises instructions for decomposing a particular polarization component of an image into its spectral components and instructions for applying a correction function to at least one spectral component. The correction function can correspond to at least one polarization dependent property.

  [00083] Conveniently, the computer readable code includes instructions for applying the correction function to a single spectral component.

  [00084] Conveniently, the reticle includes a repeating pattern, and the computer readable code includes instructions for applying the correction function to a single spectral component corresponding to a pitch of the repeating pattern.

  [00085] Conveniently, the computer readable code includes instructions for applying the correction function to a single spectral component corresponding to the pitch of the repeating pattern.

  [00086] Conveniently, the computer readable code includes instructions for applying a correction function to the spectral component that is inversely proportional to the square of the spectral frequency of the spectral component.

  [00087] Conveniently, the correction function can correspond to the angle between incident lines.

  [00088] Conveniently, the computer readable code comprises a plurality of detection channels, each characterized by a different polarization characteristic determined by controlling the polarization and intensity of light at the collection pupil plane. Contains instructions for use.

  [00089] Conveniently, the computer readable code obtains the plurality of images and instructions for changing the polarization characteristics of the illumination channel by controlling the polarization and intensity of light at the illumination pupil plane. Including.

  [00090] Conveniently, the computer readable code includes instructions for changing the polarization characteristics of the detection and illumination channels by controlling the polarization and intensity of light at the pupil plane.

  [00091] Conveniently, the computer readable code includes instructions for estimating a critical dimension of a member of a wafer produced by the exposure process.

  [00092] Conveniently, the computer readable code includes instructions for estimating a critical dimension of the reticle member.

  [00093] Conveniently, the computer readable code includes instructions for evaluating a process window of the exposure process.

  [00094] Conveniently, the computer readable code includes instructions for determining out-of-focus polarization characteristics of the imaging process in response to focus measurements.

  [00095] Conveniently, the computer readable code includes instructions for generating a defect map for the reticle.

  [00096] Conveniently, the computer readable code includes instructions for generating the output aerial image in response to phase delay characteristics of the exposure and imaging processes.

  [00097] Those skilled in the art will appreciate that various changes and modifications may be made to the embodiments of the invention as defined herein above without departing from the scope defined by and defined by the appended claims. It will be easily understood correctly that it can be applied to.

The difference between the p-polarized component and the s-polarized component passing through the exposure system is illustrated. The difference between the p-polarized component and the s-polarized component passing through the exposure system is illustrated. 1 illustrates a system according to an embodiment of the invention. 2 illustrates a method according to an embodiment of the invention. Fig. 4 illustrates the relationship between the spectral components of the s-polarized component of the intermediate image and the attenuation of those spectral components according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 14 ... Mask, 80 ... Imaging system, 81 ... Illumination channel, 82 ... Light source, 83 ... Polarizer, 87 ... Condensing lens, 91 ... Condensing channel, 92 ... Objective lens, 93 ... Camera, 95 ... Memory | storage device, 96 ... processor, 99 ... display.

Claims (12)

A method for spatial imaging comprising:
Obtaining multiple images of the reticle under different polarization conditions during the imaging process;
Generating an output aerial image of the reticle that simulates the result of the exposure process in response to a difference between the (i) the plurality of images and the imaging process and the exposure process;
A method comprising:   The method of claim 1, wherein the generating step can correspond to polarization-dependent characteristics of the exposure process and the imaging process. The generating step comprises:
Decomposing a specific polarization component of at least one of the plurality of images into its plurality of spectral components;
Applying a correction function to at least one spectral component of the plurality of spectral components, wherein the correction function can correspond to at least one polarization dependent property;
The method of claim 2 comprising:   4. The reticle of claim 3, wherein the reticle comprises a repeating pattern and generating the one output aerial image comprises applying the correction function to a single spectral component corresponding to a pitch of the repeating pattern. Method.   The method of claim 4, further comprising applying a correction function to the single spectral component that is inversely proportional to the square of the spectral frequency of the single spectral component.   2. The obtaining step of claim 1, wherein the obtaining step comprises using a plurality of detection channels, each characterized by a different polarization property determined by controlling the polarization and intensity of light at the collection pupil plane. the method of. A system for spatial imaging,
A storage device adapted to store information representing a plurality of images of the reticle;
A processor coupled to the storage device for receiving information representing the plurality of images acquired under different polarization conditions during an imaging process; (i) the plurality of images; and (ii) the imaging process; A processor adapted to generate one output aerial image of the reticle that simulates the result of the exposure process in response to a difference in the exposure process ;
A system comprising:   The system of claim 7, wherein the processor is further adapted to generate the output aerial image in response to polarization dependent characteristics of the exposure process and the imaging process.   The processor decomposes a particular polarization component of at least one image of the plurality of images into its plurality of spectral components and applies a correction function to at least one of the plurality of spectral components. The system of claim 8, further adapted, wherein the correction function can correspond to at least one of a plurality of polarization dependent properties.   The system of claim 9, wherein the reticle comprises a repeating pattern, and wherein the processor is further adapted to apply the correction function to a single spectral component corresponding to a pitch of the repeating pattern. A method for spatial imaging comprising:
Controlling an intensity and polarization of a plurality of rays during an imaging process to acquire an aerial image of the reticle to define a reticle illumination condition substantially equal to the reticle illumination condition during an exposure process;
Obtaining the aerial image of the reticle from the plurality of rays.   Applying an imaging process to obtain an aerial image of the reticle and controlling the intensity and polarization of a plurality of rays during the imaging process to provide a reticle illumination condition substantially equal to the reticle illumination condition during the exposure process. An imaging optics adapted to define; and a sensor adapted to obtain the aerial image of the reticle from the plurality of rays.