Patent Description:
Semiconductor fabrication lines typically incorporate metrology measurements at one or more points during a fabrication process to monitor and control the fabrication of features on a particular sample and/or across multiple samples. For example, a typical fabrication process includes fabricating multiple dies distributed across the surface of a sample (e.g., a semiconductor wafer, or the like), where each die includes multiple patterned layers of material forming a device component. Each patterned layer may be formed by a series of steps including material deposition, lithography, and etching to generate a pattern of interest. Further, lithography tools used in the exposure steps (e.g., a scanner, a stepper, or the like) have a field of view substantially smaller than the size of the sample such that each sample layer is exposed with many exposure fields distributed across the sample. It may thus be desirable to monitor and control field-to-field errors associated with the size and placement of exposure fields across the sample to expose each layer as well as overlay errors associated with features on different sample layers within each exposure field, which increases the number of metrology targets on a sample and decreases the fabrication throughput. However, typical metrology systems require separate targets and/or measurement techniques for overlay metrology and field-to-field metrology. It is therefore desirable to provide systems and methods for high-throughput overlay and field-to-field metrology.

<CIT> discloses a method and apparatus for self-referenced wafer stage positional error mapping.

<CIT> describes a method of determining stitching errors in multiple lithographically exposed fields on a semiconductor layer during a semiconductor manufacturing process.

<CIT> discloses a method for overlay control system.

<CIT> describes a calibration method for a lithographic apparatus.

<CIT> illustrates an overlay control systems with a layer-to-layer feedforward control and with alignment corrections.

A metrology system as recited in claim <NUM> is disclosed.

A metrology method as recited in claim <NUM> is provided.

The present disclosure has been particularly shown and described with respect to certain embodiments and specific features thereof.

Embodiments of the present disclosure are directed to systems and methods for providing overlay metrology and field-to-field metrology on a common metrology target (e.g., field-sensitive overlay metrology). Field-sensitive overlay metrology may utilize either new or conventional overlay measurement techniques on field-sensitive overlay targets to provide data indicative of overlay and/or field-to-field errors. For example, the relative positions of features on a field-sensitive overlay metrology target may be sensitive not only to variations between overlapping exposures in a common exposure field as is the case with a typical overlay target, but also to variations between adjacent exposure fields to provide data indicative of field-to-field variations.

For the purposes of the present disclosure, the term overlay metrology broadly refers to measurements of misalignment of features formed through two or more exposures on a common portion of the sample. In this regard, overlay metrology may provide measurements of the alignment of features formed on two or more layers on a sample as well as measurements of the alignment of features formed through successive exposures on a common sample layer (e.g., double patterning, triple patterning, or the like). Further, for the purposes of the present disclosure, the term field-to-field metrology broadly refers to measurements of differences between features formed in two or more exposures in different fields on the sample (e.g., adjacent fields). For example, field-to-field errors may include, but are not limited to, errors in registration or scaling between fields. Accordingly, the systems and methods disclosed herein may provide metrology measurements for a wide range of process errors in a common measurement step.

Some embodiments of the present disclosure are directed to field-sensitive overlay targets suitable for simultaneously providing data indicative of overlay and field-to-field errors. It is recognized herein that typical overlay metrology targets are formed by forming different portions of the target through multiple exposures of the same area of the sample (e.g., the same exposure field of a lithography tool) either on the same layer or different layers. In this regard, the relative positions and/or sizes of features formed in the different exposures are indicative of alignment errors of the lithography tool to the exposure field for the repeated exposures. In contrast, field-sensitive overlay targets may be formed through multiple exposures of a common portion of the sample, where at least one exposure field only partially overlaps one or more other exposure fields used to generate the target. For example, one or more features of the metrology target may be formed from exposing a first field on the sample and one or more features may be formed from exposing a second field on the sample, where the second field only partially overlaps the first field at the location of the metrology target. In this regard, relative positions and/or sizes of features in the field-sensitive overlay target are sensitive to, among other things, field-to-field variations of the various exposure fields used to generate the target.

It is contemplated herein that a field-sensitive overlay target may generally have the same design as any non-field-sensitive overlay target. For example, overlay metrology target designs suitable for adaption include image-based metrology targets such as, but not limited to, advanced imaging metrology (AIM) targets, AIM in-die (AlMid) targets, box-in-box targets, or multi-layer AIMid (MLAIMid) targets. By way of another example, overlay metrology target designs suitable for adaption include scatterometry-based overlay (SCOL) targets. Accordingly, a field-sensitive overlay target may be measured and characterized by any new or existing overlay metrology tool. However, metrology algorithms used to extract information about sources of error associated with measurements of the field-sensitive overlay targets may differ to account for the different sources of error measured by the field-sensitive overlay target.

Additional embodiments of the present disclosure are directed to photomasks suitable for fabricating field-sensitive overlay targets. For example, a photomask may include a device area including patterns associated with device features and one or more target areas surrounding the device area. In particular, target areas on opposite sides of the device area may include complementary portions of a field-sensitive overlay target. In this regard, a full layer of a field-sensitive overlay target may be fabricated by overlapping exposures on the sample (e.g., overlapping exposure fields), where the amount of overlap is designed to generate a complete pattern of the field-sensitive overlay target.

The invention is directed to generating correctables for the lithography tool based on both overlay data and field-to-field data generated using field-sensitive overlay targets. Feed-forward correctables are provided to the lithography tool during the exposure of subsequent layers to compensate for measured variations on a current layer. By way of another example, feedback correctables may be provided to the lithography tool to mitigate variations (e.g., drifts) over time.

It is further contemplated herein that field-sensitive overlay metrology may be suitable for measuring, controlling, and/or mitigating various sources of fabrication errors including, but not limited to, variations in the shape of the photomask and/or the sample, stresses on the photomask and/or the sample, surface tension effects on the photomask and/or the sample, or errors associated with the lithography tool itself. Accordingly, correctables based on field-sensitive overlay measurements may provide highly accurate and efficient control of the lithography process.

Referring now to <FIG>, systems and methods for field-sensitive overlay metrology are described in greater detail in accordance with one or more embodiments of the present disclosure.

<FIG> is a conceptual view illustrating a fabrication system <NUM>, in accordance with one or more embodiments of the present disclosure. In one embodiment, the system <NUM> includes including a lithography sub-system <NUM> for lithographically imaging one or more pattern elements on a pattern mask (e.g., device pattern elements, metrology target pattern elements, or the like) on a sample. The lithography sub-system <NUM> may include any lithographic tool known in the art such as, but not limited to, a scanner or stepper. In another embodiment, the system <NUM> includes a metrology sub-system <NUM> to characterize one or more features on the sample. The metrology sub-system <NUM> may include an overlay metrology tool suitable for measuring relative positions of sample features (e.g., features of a field-sensitive overlay target). In one embodiment, the metrology sub-system <NUM> includes an image-based metrology tool to measure metrology data based on the generation of one or more images of a sample. In another embodiment, the metrology sub-system <NUM> includes a scatterometry-based metrology system to measure metrology data based on the scattering (reflection, diffraction, diffuse scattering, or the like) of light from the sample. In another embodiment, the system <NUM> includes a controller <NUM>. In another embodiment, the controller <NUM> includes one or more processors <NUM> configured to execute program instructions maintained on a memory medium <NUM>. In this regard, the one or more processors <NUM> of controller <NUM> may execute any of the various process steps described throughout the present disclosure.

The one or more processors <NUM> of a controller <NUM> may include any processing element known in the art. In this sense, the one or more processors <NUM> may include any microprocessor-type device configured to execute algorithms and/or instructions. In one embodiment, the one or more processors <NUM> may consist of a desktop computer, mainframe computer system, workstation, image computer, parallel processor, or any other computer system (e.g., networked computer) configured to execute a program configured to operate the system <NUM>, as described throughout the present disclosure. It is further recognized that the term "processor" may be broadly defined to encompass any device having one or more processing elements, which execute program instructions from a non-transitory memory medium <NUM>. Further, the steps described throughout the present disclosure may be carried out by a single controller <NUM> or, alternatively, multiple controllers. Additionally, the controller <NUM> may include one or more controllers housed in a common housing or within multiple housings. In this way, any controller or combination of controllers may be separately packaged as a module suitable for integration into system <NUM>. Further, the controller <NUM> may analyze data received from the detector <NUM> and feed the data to additional components within the system <NUM> (e.g., the lithography sub-system <NUM>) or external to the system <NUM>.

The memory medium <NUM> may include any storage medium known in the art suitable for storing program instructions executable by the associated one or more processors <NUM>. For example, the memory medium <NUM> may include a non-transitory memory medium. By way of another example, the memory medium <NUM> may include, but is not limited to, a read-only memory, a random-access memory, a magnetic or optical memory device (e.g., disk), a magnetic tape, a solid-state drive and the like. It is further noted that memory medium <NUM> may be housed in a common controller housing with the one or more processors <NUM>. In one embodiment, the memory medium <NUM> may be located remotely with respect to the physical location of the one or more processors <NUM> and controller <NUM>. For instance, the one or more processors <NUM> of controller <NUM> may access a remote memory (e.g., server), accessible through a network (e.g., internet, intranet and the like). Therefore, the above description should not be interpreted as a limitation on the present invention but merely an illustration.

<FIG> is a conceptual view illustrating the lithography sub-system <NUM>, in accordance with one or more embodiments of the present disclosure. In one embodiment, the lithography sub-system <NUM> includes a lithography illumination source <NUM> configured to generate an illumination beam <NUM>. The one or more illumination beams <NUM> may include one or more selected wavelengths of light including, but not limited to, ultraviolet (UV) radiation, visible radiation, or infrared (IR) radiation.

Illumination from the lithography illumination source <NUM> may have any spatial distribution (e.g., illumination pattern). For example, the lithography illumination source <NUM> may include, but is not limited to, a single-pole illumination source, a dipole illumination source, a C-Quad illumination source, a Quasar illumination source, or a free-form illumination source. In this regard, the lithography illumination source <NUM> may generate on-axis illumination beams <NUM> in which illumination propagates along (or parallel to) an optical axis <NUM> and/or any number of off-axis illumination beams <NUM> in which illumination propagates at an angle to the optical axis <NUM>.

It is further noted herein that, for the purposes of the present disclosure, an illumination pole of the lithography illumination source <NUM> may represent illumination from a specific location. In this regard, each spatial location of the lithography illumination source <NUM> (e.g., with respect to the optical axis <NUM>) may be considered an illumination pole. Further, an illumination pole may have any shape or size known in the art. Additionally, the lithography illumination source <NUM> may be considered to have an illumination profile corresponding to a distribution of illumination poles.

Further, the lithography illumination source <NUM> may generate the illumination beams <NUM> by any method known in the art. For an example, an illumination beam <NUM> may be formed as illumination from an illumination pole of the lithography illumination source <NUM> (e.g., a portion of an illumination profile of a lithography illumination source <NUM>, or the like). By way of another example, lithography illumination source <NUM> may include multiple illumination sources for the generation of multiple illumination beams <NUM>.

In another embodiment, the lithography sub-system <NUM> includes a mask support device <NUM>. The mask support device <NUM> is configured to secure a pattern mask <NUM>. In another embodiment, the lithography sub-system <NUM> includes a set of projection optics <NUM> configured to project an image of the pattern mask <NUM> illuminated by the one or more illumination beams <NUM> onto a sample <NUM> disposed on a sample stage <NUM> in order to generate printed pattern elements corresponding to the image of the pattern mask <NUM>. In another embodiment, the mask support device <NUM> may be configured to actuate or position the pattern mask <NUM>. For example, the mask support device <NUM> may actuate the pattern mask <NUM> to a selected position with respect to the projection optics <NUM> of the system <NUM>.

The sample <NUM> may include any number of photosensitive materials and/or material layers suitable for receiving the image of the pattern mask <NUM>. For example, the sample <NUM> may include a resist layer <NUM>. In this regard, the set of projection optics <NUM> may project an image of the pattern mask <NUM> onto the resist layer <NUM> to expose the resist layer <NUM> and a subsequent etching step may remove the exposed material (e.g., positive etching) or the unexposed material (e.g., negative etching) in order to provide printed features on the sample <NUM>. Further, the pattern mask <NUM> may be utilized in any imaging configuration known in the art. For example, the pattern mask <NUM> may be a positive mask (e.g., a bright-field mask) in which pattern elements are positively imaged as printed pattern elements. By way of another example, the pattern mask <NUM> may be a negative mask (e.g., a dark-field mask) in which pattern elements of the pattern mask <NUM> form negative printed pattern elements (e.g., gaps, spaces, or the like).

The controller <NUM> may be communicatively coupled any element or combination of elements in the lithography sub-system <NUM> such as, but not limited to, the mask support device <NUM> and/or the sample stage <NUM> to direct the transfer of pattern elements on a pattern mask <NUM> to a sample <NUM>, the lithography illumination source <NUM> to control one or more characteristics of the illumination beam <NUM>.

<FIG> is a block diagram view of the metrology sub-system <NUM>, in accordance with one or more embodiments of the present disclosure. The system <NUM> may generate one or more images associated with light emanating from the sample <NUM> (e.g., sample light <NUM>) on at least one detector <NUM> using any method known in the art. In one embodiment, the detector <NUM> is located at a field plane to generate an image of one or more features on the sample <NUM>. In this regard, the system <NUM> may operate as an image-based overlay metrology tool. In another embodiment, the detector <NUM> is located at a pupil plane to generate an image based on angles of light emanating from the sample <NUM> (e.g., based on reflection, diffraction, scattering, or the like). In this regard, the system <NUM> may operate as a scatterometry-based metrology tool.

In one embodiment, the metrology sub-system <NUM> includes a metrology illumination source <NUM> to generate a metrology illumination beam <NUM>. The metrology illumination source <NUM> may be the same as the lithography illumination source <NUM> or may be a separate illumination source configured to generate a separate metrology illumination beam <NUM>. The metrology illumination beam <NUM> may include one or more selected wavelengths of light including, but not limited to, vacuum ultraviolet (VUV) radiation, deep ultraviolet (DUV) radiation, ultraviolet (UV) radiation, visible radiation, or infrared (IR) radiation. The metrology illumination source <NUM> may further generate a metrology illumination beam <NUM> including any range of selected wavelengths. In another embodiment, the metrology illumination source <NUM> may include a spectrally-tunable illumination source to generate a metrology illumination beam <NUM> having a tunable spectrum.

The metrology illumination source <NUM> may further produce a metrology illumination beam <NUM> having any temporal profile. For example, the metrology illumination source <NUM> may produce a continuous metrology illumination beam <NUM>, a pulsed metrology illumination beam <NUM>, or a modulated metrology illumination beam <NUM>. Additionally, the metrology illumination beam <NUM> may be delivered from the metrology illumination source <NUM> via free-space propagation or guided light (e.g., an optical fiber, a light pipe, or the like).

In another embodiment, the metrology illumination source <NUM> directs the metrology illumination beam <NUM> to the sample <NUM> via an illumination pathway <NUM>. The illumination pathway <NUM> may include one or more lenses <NUM> or additional illumination optical components <NUM> suitable for modifying and/or conditioning the metrology illumination beam <NUM>. For example, the one or more illumination optical components <NUM> may include, but are not limited to, one or more polarizers, one or more filters, one or more beam splitters, one or more diffusers, one or more homogenizers, one or more apodizers, one or more beam shapers, or one or more shutters (e.g., mechanical shutters, electro-optical shutters, acousto-optical shutters, or the like). By way of another example, the one or more illumination optical components <NUM> may include aperture stops to control the angle of illumination on the sample <NUM> and/or field stops to control the spatial extent of illumination on the sample <NUM>. In one instance, the illumination pathway <NUM> includes an aperture stop located at a plane conjugate to the back focal plane of an objective lens <NUM> to provide telecentric illumination of the sample. In another embodiment, the system <NUM> includes an objective lens <NUM> to focus the metrology illumination beam <NUM> onto the sample <NUM>.

In another embodiment, the sample <NUM> is disposed on a sample stage <NUM>. The sample stage <NUM> may include any device suitable for positioning the sample <NUM> within the system <NUM>. For example, the sample stage <NUM> may include any combination of linear translation stages, rotational stages, tip/tilt stages, or the like.

In another embodiment, a detector <NUM> is configured to capture radiation emanating from the sample <NUM> (e.g., sample light <NUM>) through a collection pathway <NUM>. For example, the collection pathway <NUM> may include, but is not required to include, a collection lens (e.g., the objective lens <NUM> as illustrated in <FIG>) or one or more additional collection pathway lenses <NUM>. In this regard, a detector <NUM> may receive radiation reflected or scattered (e.g., via specular reflection, diffuse reflection, and the like) from the sample <NUM> or generated by the sample <NUM> (e.g., luminescence associated with absorption of the metrology illumination beam <NUM>, or the like).

The collection pathway <NUM> may further include any number of collection optical components <NUM> to direct and/or modify illumination collected by the objective lens <NUM> including, but not limited to, one or more collection pathway lenses <NUM>, one or more filters, one or more polarizers, or one or more beam blocks. Additionally, the collection pathway <NUM> may include field stops to control the spatial extent of the sample imaged onto the detector <NUM> or aperture stops to control the angular extent of illumination from the sample used to generate an image on the detector <NUM>. In another embodiment, the collection pathway <NUM> includes an aperture stop located in a plane conjugate to the back focal plane of an optical element the objective lens <NUM> to provide telecentric imaging of the sample.

The detector <NUM> may include any type of optical detector known in the art suitable for measuring illumination received from the sample <NUM>. For example, a detector <NUM> may include a sensor suitable for generating one or more images of a static sample <NUM> (e.g., in a static mode of operation) such as, but is not limited to, a charge-coupled device (CCD), a complementary metal-oxide-semiconductor (CMOS) sensor, a photomultiplier tube (PMT) array, or an avalanche photodiode (APD) array. By way of another example, a detector <NUM> may include a sensor suitable for generating one or more images of a sample <NUM> in motion (e.g., a scanning mode of operation) such as, but not limited to, a line sensor or a time delay and integration (TDI) sensor.

In another embodiment, a detector <NUM> may include a spectroscopic detector suitable for identifying wavelengths of radiation emanating from the sample <NUM>. In another embodiment, the system <NUM> may include multiple detectors <NUM> (e.g., associated with multiple beam paths generated by one or more beamsplitters) to facilitate multiple metrology measurements by the system <NUM>.

In one embodiment, as illustrated in <FIG>, the system <NUM> includes a beamsplitter <NUM> oriented such that the objective lens <NUM> may simultaneously direct the metrology illumination beam <NUM> to the sample <NUM> and collect radiation emanating from the sample <NUM>. In this regard, the system <NUM> may be configured in an epi-illumination mode.

In another embodiment, the controller <NUM> is communicatively coupled to one or more elements of the system <NUM>. In this regard, the controller <NUM> may transmit and/or receive data from any component of the system <NUM>. For example, the controller <NUM> may be configured to receive data including, but not limited to, one or more images from the detector <NUM>.

<FIG> is a conceptual top view of a sample <NUM> illustrating a multitude of overlapping exposure fields <NUM> associated with multiple lithography steps by the lithography sub-system <NUM> associated with fabrication of a particular sample layer, in accordance with one or more embodiments of the present disclosure. In one embodiment, a pattern mask <NUM> is imaged onto each exposure field <NUM>. Further, the same pattern mask <NUM> may be repeatedly imaged onto each exposure field <NUM> or multiple pattern masks <NUM> may be imaged onto selected exposure fields <NUM>. It is to be understood, however, that <FIG> is not drawn to scale. Rather, parameters in <FIG> such as, but not limited to, the size of each exposure field <NUM> relative to the size of the sample <NUM>, the number of exposure fields <NUM>, or the amount of overlap between adjacent exposure fields <NUM> are selected for illustrative purposes and should not be interpreted as limiting.

In one embodiment, as illustrated in <FIG>, adjacent exposure fields <NUM> may overlap to form overlap regions <NUM> distributed across the sample <NUM>. Device features (e.g., associated with dies distributed across the sample <NUM>) may be fabricated in any of the non-overlap regions <NUM>, whereas field-sensitive overlay targets, or portions thereof on a particular sample layer, may be formed in any of the overlap regions <NUM> based on exposures from adjacent, overlapping exposure fields <NUM>. In contrast, it is recognized herein that typical overlay metrology targets may be formed using fully-overlapping exposure fields <NUM> associated with different lithography steps either on the same layer or on different layers.

In another embodiment, the pattern of exposure fields <NUM> may be replicated for multiple lithography steps associated in a fabrication process. For example, a first set of pattern elements associated with a first sample layer may be fabricated using a series of material deposition steps, lithography steps using a pattern of exposure fields <NUM> (e.g., as illustrated in <FIG>), etching steps, and the like. A second set of pattern elements associated with a second sample layer may be fabricated using an additional series of material deposition steps, lithography steps using a pattern of exposure fields <NUM>, etching steps, and the like, where the pattern of exposure fields <NUM> associated with the first and second sample layers are aligned. A similar process may be carried out for multiple aligned exposures on a single sample layer (e.g., for a double-patterning process, or the like).

Referring now to <FIG>, field-sensitive metrology targets and their formation are described in greater detail in accordance with one or more embodiments of the present disclosure. It is contemplated herein that field-sensitive metrology targets may include features on any number of sample layers formed from any number of overlapping exposure fields <NUM>. <FIG> illustrate non-limiting examples of two-layer field-sensitive overlay targets in which features associated with a first sample layer are formed using one exposure field <NUM> and features associated with a second layer are formed using an adjacent overlapping exposure field <NUM>. In these designs, relative positions and/or sizes of the first-layer features with respect to the second-layer features are sensitive to, among other things, field-to-field variations between lithography steps associated with different sample layers. <FIG> illustrate a non-limiting example of a one-layer field-sensitive overlay target. In this design, relative positions and/or sizes of the first-layer features with respect to the second-layer features are sensitive to, among other things, field-to-field variations between lithography steps associated with a single sample layer. <FIG> illustrate a non-limiting example of a two-layer field-sensitive overlay target formed using four exposures across two exposure fields <NUM>: first-layer features are fabricated using adjacent exposure fields <NUM> in a manner similar to the illustration in <FIG>, and second-layer features are fabricated using the same adjacent exposure fields <NUM> used for the first-layer features. In this design, portions of the target including features on different layers formed from fully overlapping exposure fields <NUM> may operate as traditional overlay targets and provide data indicative of errors in alignment and/or scaling of the lithography tool for successive exposures of the respective exposure field <NUM>. Further, portions of the target including features formed from partially-overlapping exposure fields <NUM> may provide data indicative of field-to-field errors. Further, it is to be understood that the examples herein are provided solely for illustrative purposes and should not be interpreted as limiting. By way of another example, field-sensitive overlay targets may include features on three or more sample layers formed with at least one exposure field <NUM> that only partially overlaps other exposure fields <NUM> at the target location.

<FIG> is a conceptual top view of a two-layer field-sensitive overlay target <NUM>, in accordance with one or more embodiments of the present disclosure. In one embodiment, the field-sensitive overlay target <NUM> includes first-layer target features <NUM> formed with a first exposure field <NUM> and second-layer target features <NUM> formed with a second exposure field, where the second exposure field <NUM> only partially overlaps the first exposure field <NUM>. For example, using the illustration of <FIG>, the first-layer target features <NUM> may be associated with the exposure field 202a and the second-layer target features <NUM> may be associated with the exposure field 202b. The first-layer target features <NUM> and the second-layer target features <NUM> are thus complementary portions of the full field-sensitive overlay target <NUM>.

It is to be understood that the layout of the field-sensitive overlay target <NUM> in <FIG> is intended to be illustrative rather than limiting. The first-layer target features <NUM> and the second-layer target features <NUM> may be arranged in any configuration suitable for an overlay measurement. For example, the layout of the first-layer target features <NUM> and the second-layer target features <NUM> is not limited to the depiction in <FIG> where the first-layer target features <NUM> and the second-layer target features <NUM> each include two cells and are distributed along crossed diagonals. Rather, the first-layer target features <NUM> and the second-layer target features <NUM> may distributed in any number of cells in any pattern suitable for overlay measurements. In one instance, the first-layer target features <NUM> and the second-layer target features <NUM> may fully or partially overlap. Further, any of the first-layer target features <NUM> or the second-layer target features <NUM> may be segmented along one or more directions.

Accordingly, it is further contemplated herein that any technique may be used to determine the relative positions of features formed from different exposures, which may be influenced by a variety of sources of error including overlay errors and field-to-field errors as described previously herein. For example, the positions of the first-layer target features <NUM> may be directly compared to the second-layer target features <NUM>. By way of another example, centers of symmetry (e.g., rotational symmetry, reflective symmetry, or the like) associated with first-layer target features <NUM> and the second-layer target features <NUM> may be compared.

<FIG> illustrate various designs of the field-sensitive overlay target <NUM> illustrated in <FIG>, as well as associated pattern masks <NUM> suitable for fabricating the various designs using adjacent partially-overlapping exposure fields <NUM>. It is to be understood, however, that the designs of the field-sensitive overlay target <NUM> illustrated in <FIG> are provided solely for illustrative purposes and should not be interpreted as limiting. It is contemplated herein that any overlay target design may be adapted to be field-sensitive by fabricating complementary portions using adjacent partially-overlapping exposure fields <NUM>.

<FIG> is a top view of a pattern mask <NUM> (e.g., corresponding to the pattern mask <NUM> in <FIG>) suitable for forming the field-sensitive overlay target <NUM> illustrated in <FIG>, in accordance with one or more embodiments of the present disclosure. In one embodiment, the pattern mask <NUM> includes a device area <NUM> including a pattern of device features (not shown) associated with a semiconductor device being fabricated. In another embodiment, the pattern mask <NUM> includes complementary portions of the field-sensitive overlay target <NUM> on opposing sides of the device area <NUM>, but within a boundary <NUM> of an imaged area. For example, the pattern mask <NUM> includes complementary portions of the field-sensitive overlay target <NUM> along a horizontal axis for the formation of a full field-sensitive overlay target <NUM> with exposure fields <NUM> adjacent along the horizontal direction and also includes complementary portions of the field-sensitive overlay target <NUM> along a vertical axis for the formation of a full field-sensitive overlay target <NUM> with exposure fields <NUM> adjacent along the vertical direction. In particular, pattern elements <NUM> associated with the first-layer target features <NUM> are located on the left and top sides of the device area <NUM> and pattern elements <NUM> associated with the second-layer target features <NUM> are located on the right and bottom sides of the device area <NUM>.

<FIG> is a top view of a portion of the sample <NUM> illustrating the fabrication of field-sensitive overlay targets <NUM> based on the pattern mask <NUM> of <FIG> along two orthogonal directions with overlapping exposure fields <NUM>, in accordance with one or more embodiments of the present disclosure. In one embodiment, each exposure field <NUM> includes an image of the pattern mask <NUM>. Further, the spacing and amount of overlap between adjacent exposure fields <NUM> may be selected such that the complementary portions of the field-sensitive overlay target <NUM> overlap on the sample <NUM> to form the full field-sensitive overlay target <NUM> in an overlap region <NUM>, whereas device features associated with the device area <NUM> of the pattern mask <NUM> are formed in non-overlap regions <NUM>.

For example, the field-sensitive overlay target 300a is formed using first-layer target features <NUM> from a first exposure field <NUM> (e.g., exposure field 202a) and second-layer target features <NUM> from a second exposure field <NUM> (e.g., exposure field 202b). By way of another example, the field-sensitive overlay target 300b is formed using the first-layer target features <NUM> from the first exposure field <NUM> (e.g., exposure field 202a) and the second-layer target features <NUM> from a third exposure field <NUM> (e.g., exposure field 202c).

Referring now to <FIG>, various designs of the field-sensitive overlay target, as well as the associated pattern masks, are described in greater detail, in accordance with one or more embodiments of the present disclosure. The descriptions associated with the pattern mask <NUM> and partially-overlapping exposures of the pattern mask <NUM> on the sample <NUM> to fabricate field-sensitive overlay targets <NUM> associated with <FIG> may be applied to the target designs illustrated in <FIG>.

<FIG> is a top view of a pattern mask <NUM> (e.g., corresponding to the pattern mask <NUM> in <FIG>) suitable for forming a design of the field-sensitive overlay target <NUM> illustrated in <FIG> including four cells, where portion of the first-layer target features <NUM> and the second-layer target features <NUM> are located in each cell, in accordance with one or more embodiments of the present disclosure. In particular, pattern elements <NUM> associated with the first-layer target features <NUM> are located on the left and bottom sides of the device area <NUM> and pattern elements <NUM> associated with the second-layer target features <NUM> are located on the right and top sides of the device area <NUM>. <FIG> is a top view of a portion of the sample <NUM> illustrating the fabrication of the field-sensitive overlay targets <NUM> based on the pattern mask <NUM> in <FIG> along two orthogonal directions with partially-overlapping exposure fields <NUM>, in accordance with one or more embodiments of the present disclosure. The relative positions of the first-layer target features <NUM> and the second-layer target features <NUM> in this design may be, but are not required to be, determined by comparison of the respective centers of rotational symmetry. For example, the first-layer target features <NUM> and the second-layer target features <NUM> exhibit <NUM>-degree rotational symmetry.

<FIG> is a top view of a pattern mask <NUM> (e.g., corresponding to the pattern mask <NUM> in <FIG>) suitable for forming a box-in-box design of the field-sensitive overlay target <NUM> illustrated in <FIG> in which portions of the first-layer target features <NUM> and the second-layer target features <NUM> are located in a series of nested boxes, in accordance with one or more embodiments of the present disclosure. <FIG> is a top view of a portion of the sample <NUM> illustrating the fabrication of the field-sensitive overlay targets <NUM> based on the pattern mask <NUM> in <FIG> with partially-overlapping exposure fields <NUM>, in accordance with one or more embodiments of the present disclosure. Although not shown, a field-sensitive overlay target <NUM> may be formed through partially-overlapping exposures of the pattern mask <NUM> along the vertical direction in <FIG> in a similar manner is illustrated in <FIG> and <FIG>.

<FIG> is a top view of a pattern mask <NUM> (e.g., corresponding to the pattern mask <NUM> in <FIG>) suitable for forming a "Ruller"-type design of the field-sensitive overlay target <NUM> illustrated in <FIG> in which portions of the first-layer target features <NUM> and the second-layer target features <NUM> are located in a series of nested combs, in accordance with one or more embodiments of the present disclosure. <FIG> is a top view of a portion of the sample <NUM> illustrating the fabrication of the field-sensitive overlay targets <NUM> based on the pattern mask <NUM> in <FIG> with partially-overlapping exposure fields <NUM>, in accordance with one or more embodiments of the present disclosure. Although not shown, a field-sensitive overlay target <NUM> may be formed through partially-overlapping exposures of the pattern mask <NUM> along the vertical direction in <FIG> in a similar manner is illustrated in <FIG> and <FIG>.

<FIG> is a top view of a pattern mask <NUM> (e.g., corresponding to the pattern mask <NUM> in <FIG>) suitable for forming an AIMid design of the field-sensitive overlay target <NUM> illustrated in <FIG> in which the first-layer target features <NUM> and the second-layer target features <NUM> are interleaved, in accordance with one or more embodiments of the present disclosure. <FIG> is a top view of a portion of the sample <NUM> illustrating the fabrication of the field-sensitive overlay targets <NUM> based on the pattern mask <NUM> in <FIG> with partially-overlapping exposure fields <NUM>, in accordance with one or more embodiments of the present disclosure. Although not shown, a field-sensitive overlay target <NUM> may be formed through partially-overlapping exposures of the pattern mask <NUM> along the vertical direction in <FIG> in a similar manner is illustrated in <FIG> and <FIG>.

<FIG> is a top view of a pattern mask <NUM> (e.g., corresponding to the pattern mask <NUM> in <FIG>) suitable for forming an AIMid design of the field-sensitive overlay target <NUM> illustrated in <FIG> in which the first-layer target features <NUM> and the second-layer target features <NUM> overlap to form cross patterns, in accordance with one or more embodiments of the present disclosure. <FIG> is a top view of a portion of the sample <NUM> illustrating the fabrication of the field-sensitive overlay targets <NUM> based on the pattern mask <NUM> in <FIG> with partially-overlapping exposure fields <NUM>, in accordance with one or more embodiments of the present disclosure. Although not shown, a field-sensitive overlay target <NUM> may be formed through partially-overlapping exposures of the pattern mask <NUM> along the vertical direction in <FIG> in a similar manner is illustrated in <FIG> and <FIG>.

Referring now to <FIG>, a single-layer field-sensitive overlay target <NUM> is described in accordance with one or more embodiments of the present disclosure. <FIG> is a conceptual top view of a single-layer field-sensitive overlay target <NUM>, in accordance with one or more embodiments of the present disclosure. The single-layer field-sensitive overlay target <NUM> in <FIG> is similar to the two-layer field-sensitive overlay target <NUM> illustrated in <FIG>, except that all features are formed using exposure fields <NUM> associated with a common sample layer. In particular, the single-layer field-sensitive overlay target <NUM> may include a first set of target features <NUM> associated with a first exposure field <NUM> (e.g., exposure field 202a) and a second set of target features <NUM> associated with a second exposure field <NUM> (e.g., exposure field 202b or exposure field 202c).

<FIG> is a top view of a pattern mask <NUM> (e.g., corresponding to the pattern mask <NUM> in <FIG>) suitable for forming the field-sensitive overlay target <NUM> illustrated in <FIG>, in accordance with one or more embodiments of the present disclosure. In particular, pattern elements <NUM> are associated with the first set of target features <NUM> and pattern elements <NUM> are associated with the second set of target features <NUM>. <FIG> is a top view of a portion of the sample <NUM> illustrating the fabrication of the field-sensitive overlay targets <NUM> based on the pattern mask <NUM> in <FIG> along two orthogonal directions with partially-overlapping exposure fields <NUM>, in accordance with one or more embodiments of the present disclosure.

Referring now to <FIG>, a two-layer field-sensitive overlay target <NUM> is described in accordance with one or more embodiments of the present disclosure. <FIG> is a conceptual top view of a single-layer field-sensitive overlay target <NUM>, in accordance with one or more embodiments of the present disclosure.

In one embodiment, the field-sensitive overlay target <NUM> is formed from four exposures. For example, the field-sensitive overlay target <NUM> may include a first set of first-layer features <NUM> formed from a first exposure field <NUM> (e.g., exposure field 202a) and a second set of first-layer features <NUM> formed from a second exposure field <NUM> (e.g., exposure field 202b or exposure field 202c) that partially overlaps with the first exposure field <NUM>. The field-sensitive overlay target <NUM> may further include a first set of second-layer features <NUM> formed from the first exposure field <NUM> (e.g., exposure field 202a) on the second sample layer and a second set of second-layer features <NUM> formed from the second exposure field <NUM> (e.g., exposure field 202b or exposure field 202c).

<FIG> is a top view of a pattern mask <NUM> (e.g., corresponding to the pattern mask <NUM> in <FIG>) suitable for forming the first-layer features (e.g., the first set of first-layer features <NUM> and the second set of first-layer features <NUM>), in accordance with one or more embodiments of the present disclosure. In particular, pattern elements <NUM> are associated with the first set of first-layer features <NUM> and pattern elements <NUM> are associated with the second set of first-layer features <NUM>.

<FIG> is a top view of a portion of the sample <NUM> illustrating the fabrication of the first-layer features of a field-sensitive overlay target <NUM> based on the pattern mask <NUM> in <FIG> with partially-overlapping exposure fields <NUM> (e.g., exposure fields 202a,b in a lithography step for the first layer), in accordance with one or more embodiments of the present disclosure.

<FIG> is a top view of a pattern mask <NUM> (e.g., corresponding to the pattern mask <NUM> in <FIG>) suitable for forming the second-layer features (e.g., the first set of second-layer features <NUM> and the second set of second-layer features <NUM>), in accordance with one or more embodiments of the present disclosure. In particular, pattern elements <NUM> are associated with the first set of second-layer features <NUM> and pattern elements <NUM> are associated with the second set of second-layer features <NUM>.

<FIG> is a top view of a portion of the sample <NUM> illustrating the fabrication of the second-layer features of a field-sensitive overlay target <NUM> based on the pattern mask <NUM> in <FIG> with partially-overlapping exposure fields <NUM> (e.g., exposure fields 202a,b in a lithography step for the second layer), in accordance with one or more embodiments of the present disclosure. Further, the exposure fields 202a,b in a lithography step for the second layer may fully overlap the corresponding exposure fields 202a,b in a lithography step for the first layer.

<FIG> is a top view of a portion of the sample <NUM> illustrating the fabrication of the field-sensitive overlay targets <NUM> based on the pattern masks <NUM> and <NUM> in <FIG> and <FIG> along two orthogonal directions with partially-overlapping exposure fields <NUM>, in accordance with one or more embodiments of the present disclosure.

As illustrated by <FIG>, the field-sensitive overlay target <NUM> may provide both typical overlay data and field-to-field data associated with each layer and between layers. For example, since the first set of first-layer features <NUM> and the first set of second-layer features <NUM> are formed from fully overlapping exposure fields <NUM> (e.g., exposure field 202a) in the first and second layers, the relative positions and/or sizes of the first set of first-layer features <NUM> with respect to the first set of second-layer features <NUM> may be indicative of typical overlay errors provided by typical overlay targets that are associated with aligning lithography steps across multiple layers. Also, the second set of first-layer features <NUM> and the second set of second-layer features <NUM> may provide similar data.

However, the field-sensitive overlay target <NUM> may also provide data indicative of various field-to-field errors. For example, the pattern mask <NUM> of <FIG> and the pattern mask <NUM> of <FIG> both operate in a similar way as the pattern mask <NUM> illustrated in <FIG>. Accordingly, the relative positions and/or sizes of the first set of first-layer features <NUM> with respect to the second set of first-layer features <NUM> may be indicative of field-to field errors in the first layer, while the relative positions and/or sizes of the first set of second-layer features <NUM> with respect to the second set of second-layer features <NUM> may be indicative of field-to field errors in the second layer. Further, the field-sensitive overlay target <NUM> may provide data indicative of field-to-field errors spanning multiple layers. For example, the relative positions and/or sizes of the first set of first-layer features <NUM> with respect to the second set of second-layer features <NUM> may be indicative of field-to field errors spanning multiple layers similar to data provided by the targets illustrated in <FIG>. Similar data may also be obtained based on the second set of first-layer features <NUM> and the second set of second-layer features <NUM>.

As described previously herein, it is to be understood that <FIG> are provided solely for illustrative purposes and should not be interpreted as limiting. Rather, a field-sensitive overlay target may include any number of features formed through any number of exposures, where at least some of the features of the target are formed from an exposure field <NUM> that only partially overlaps other exposure fields <NUM> used to form the target. Further, a field-sensitive overlay target may include a combination of features illustrated herein. For example, a field-sensitive overlay target may include features on three or more sample layers.

<FIG> is a flow diagram illustrating steps performed in a method <NUM> for field-sensitive overlay metrology, in accordance with one or more embodiments of the present disclosure. Applicant notes that the embodiments and enabling technologies described previously herein in the context of the system <NUM> should be interpreted to extend to method <NUM>. It is further noted, however, that the method <NUM> is not limited to the architecture of the system <NUM>.

The method includes a step <NUM> of exposing a first exposure field on a sample with a lithography tool to form at least a first feature of a metrology target (e.g., a field-sensitive overlay target). Further, the method includes a step <NUM> of exposing a second exposure field on the sample with the lithography tool to form at least a second feature of the metrology target, where the second exposure field partially overlaps the first exposure field. In particular the second exposure field may overlap the first exposure field at a location of the metrology target on the sample. In this regard, the first feature of the metrology target and the second feature of the metrology target may form complementary portions of the metrology target.

It is contemplated herein that the first exposure field may be on the same layer or on a different layer than the second exposure field. Accordingly, the first feature and the second feature may be on the same or different layers of the sample. Further, the method may include additional exposures to form additional features of the metrology target, where each additional exposure either fully or partially overlaps any other exposures used to generate features of the metrology target.

For example, <FIG> illustrate various non-limiting examples of the implementation of the steps <NUM> and <NUM> using the system <NUM>.

The method includes a step <NUM> of generating metrology data associated with the metrology target with a metrology tool (e.g., the metrology sub-system <NUM>, or the like). In another embodiment, the method includes a step <NUM> of determining one or more fabrication errors during fabrication of the metrology target based on the metrology data. For example, the relative positions and/or sizes of features of the metrology target (e.g., the first feature, the second feature, any additional features, or the like) may be indicative of fabrication errors during fabrication of the metrology target such as, but not limited to, errors associated with the lithography tool (e.g., field scaling errors, field-to-field alignment errors, sample-to-mask alignment errors, overlay errors, or the like) or errors associated with the sample (e.g., sample stresses, sample imperfections, or the like).

The method includes a step <NUM> of generating one or more correctables to adjust one or more fabrication parameters of the lithography tool in one more subsequent lithography steps based on the one or more fabrication errors.

The step <NUM> includes generating correctables for use in any combination of feedback or feedforward control of the lithography tool used to fabricate the metrology target (and thus device features on the sample). Feed-forward correctables are provided to the lithography tool during the exposure of subsequent layers of the same sample to compensate for measured variations on a current sample layer. By way of another example, feedback correctables may be provided to the lithography tool to mitigate variations (e.g., drifts) over time. Such correctables may be applied to different portions of the same sample, to different samples within the same lot, or samples spread across multiple lots.

It is contemplated herein that metrology targets generated by the method <NUM> providing sensitivity to field-to-field errors (e.g., field-sensitive overlay targets) may enable the generation of more accurate and effective correctables to a lithography tool than typical overlay targets. For example, the field-sensitive metrology targets disclosed herein may facilitate determination of high-resolution reference points (HRRP) for the reduction of overlay errors between stitched target cells that originate from different exposure fields. By way of another example, the field-sensitive metrology targets disclosed herein may be printed along field edges to facilitate intra-and inter-field patterning wrap geometry measurements (PWG) or assist in fine-tuning or verification of existing PWG techniques.

The herein described subject matter sometimes illustrates different components contained within, or connected with, other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures can be implemented which achieve the same functionality. Likewise, any two components so associated can also be viewed as being "connected" or "coupled" to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being "couplable" to each other to achieve the desired functionality. Specific examples of couplable include but are not limited to physically interactable and/or physically interacting components and/or wirelessly interactable and/or wirelessly interacting components and/or logically interactable and/or logically interacting components.

Claim 1:
A metrology system (<NUM>) comprising:
a controller (<NUM>) communicatively coupled to a metrology tool (<NUM>) and a lithography tool (<NUM>), the controller including one or more processors (<NUM>) configured to execute program instructions causing the one or more processors to:
receive metrology data associated with a field-sensitive overlay metrology target fabricated according to a metrology target design, wherein the metrology target design includes at least a first feature to be formed on the sample by (<NUM>) exposing a first exposure field (<NUM>) on a first layer of the sample with the lithography tool, wherein the field-sensitive overlay metrology target design further includes at least a second feature to be formed by (<NUM>) exposing a second exposure field (<NUM>) on a second layer of the sample different than the first layer with the lithography tool,
wherein the second exposure field (<NUM>) partially overlaps the first exposure field (<NUM>),
wherein the second exposure field (<NUM>) overlaps the first exposure field (<NUM>) at a location of the field-sensitive overlay metrology target on the sample;
(<NUM>) generating metrology data associated with the field-sensitive overlay metrology target with the metrology tool (<NUM>);
(<NUM>) determine one or more fabrication errors during fabrication of the field-sensitive overlay metrology target based on the metrology data; characterized by the process step to (<NUM>) generate one or more correctables to adjust one or more fabrication parameters of the lithography tool (<NUM>) in one or more subsequent lithography steps based on the one or more fabrication errors, wherein the one or more correctables comprise feed-forward correctables which are provided to the lithography tool (<NUM>), during the exposure of subsequent layers of the same sample to compensate for fabrication errors on a current sample layer.