CPL mask and a method and program product for generating the same

A method of generating a mask for printing a pattern including a plurality of features. The method includes the steps of obtaining data representing the plurality of features; and forming at least one of the plurality of features by etching a substrate to form a mesa and depositing a chrome layer over the entire upper surface of the mesa, where said mesa has a predetermined height.

TECHNICAL FIELD

The present invention relates generally to the generation of mask patterns for use with chromeless phase lithography (CPL) techniques, and more specifically, for methods and techniques for improving imaging of critical features while simultaneously reducing the complexity of the mask making process required to produce masks capable of imaging such critical features.

BACKGROUND OF THE INVENTION

The photolithographic masks referred to above comprise geometric patterns corresponding to the circuit components to be integrated onto a silicon wafer. The patterns used to create such masks are generated utilizing CAD (computer-aided design) programs, this process often being referred to as EDA (electronic design automation). Most CAD programs follow a set of predetermined design rules in order to create functional masks. These rules are set by processing and design limitations. For example, design rules define the space tolerance between circuit devices (such as gates, capacitors, etc.) or interconnect lines, so as to ensure that the circuit devices or lines do not interact with one another in an undesirable way. The design rule limitations are typically referred to as “critical dimensions” (CD). A critical dimension of a circuit can be defined as the smallest width of a line or hole or the smallest space between two lines or two holes. Thus, the CD determines the overall size and density of the designed circuit.

Of course, one of the goals in integrated circuit fabrication is to faithfully reproduce the original circuit design on the wafer (via the mask). One technique, which is currently receiving attention from the photolithography community, for further improving the resolution/printing capabilities of photolithography equipment is referred to as chromeless phase lithography “CPL”. As is known, when utilizing CPL techniques, the resulting mask pattern typically includes structures (corresponding to features to be printed on the wafer) which do not require the use of chrome (i.e., the features are printed by phase-shift techniques) as well as those that utilize chrome. Such CPL masks have been disclosed in USP Publication No. 2004-0115539 (the '539 reference), which is herein incorporated by reference in its entirety.

As discussed in the '539 reference, for actual manufacturing purposes it was found that it was beneficial to classify the mask design features into “three zones”. Referring toFIG. 1a,Zone1features are those features with a critical dimension in the range that two phase edges (left and right) interact closely and form a single aerial image. As the two phase edges become further apart (or larger feature CD), each of the left and right phase edge form its own aerial image and the two do not interact, as shown inFIG. 1c.This type of feature is classified as a Zone3. In this case, in order to prevent the Zone3features from being printed as two separate line patterns, a piece of dark chrome is placed on the top of the substrate, and the Zone3feature forms a single aerial image as shown inFIG. 1c.In other words, the Zone3features essentially become “chrome” mask features.

In the case where the CD dimension is such that the two phase-edges partially interact as shown inFIG. 1b,these features are classified as Zone2features. However, the aerial images formed by the partial phase edge interaction are quite poor in quality, and therefore unusable. The '539 reference discloses that by tuning the percent transmission using chrome patches, it is possible to obtain high fidelity aerial image for such features. Accordingly, by classifying the randomly designed mask features into the three imaging zones, and then applying optical proximity correction (OPC) accordingly, it is possible to achieve volume IC manufacturing with a CPL mask.

FIGS. 2aand2billustrate the application of the chrome patches (referred to as the “zebra” technique) and the application of a standard alternating phase-shift mask (Alt-PSM), respectively, for Zone2features, as well as a comparison between the performance of the CPL zebra technique and the Alt-PSM technique. Referring toFIG. 2a,for Zone2features (which in the given example are three parallel lines), the quartz substrate20is etched so as to form three sets of adjacent π-phase edges and then chrome patches22are disposed on top of the features24formed by the etching so as to form strips/patches of chrome (i.e., zebra pattern) on the upper surface of the etched feature24. The duty ratio of the “zebra” pattern needs to be un-resolvable by the imaging tool so that the “zebra” essentially become digitally halftoned. In other words, the Zone2features are “shaded” phase patterns from the image tool point of view. The amount of shade (i.e., percentage transmission) is determined by the ratio between the size of the chrome patches (dark) vs. the size of the open areas (clear). By utilizing these patches, it is possible to control the percentage transmission for the Zone2mask features, and achieve high fidelity patterning.

Indeed, as shown inFIG. 2a,the “zebra’ features comfortably rival the imaging performance associated with a standard alternating PSM (AltPSM) mask26, which is illustrated inFIG. 2b,and is imaging the same three parallel line pattern as imaged by the mask inFIG. 2a.As shown, both of the resulting aerial images show excellent minimum aerial image (I-min), and better image contrast since lower I-min means it is a “darker” image that can better form a higher fidelity line pattern. However, for the Zone2features imaged utilizing the zebra CPL technique, the resulting aerial image is inherently much more symmetrical near the outer sides of the group line patterns. This is one of the major benefits of using the zebra CPL techniques because a more practicable OPC treatment is feasible. One issue with utilizing the zebra technique for implementing Zone2features in a mask is that such zebra mask features require the use of an e-beam or high-resolution mask making process. Borderline quality zebra mask patterns reduce effectiveness of transmission control during patterning. The zebra pattern can also cause difficulty in reticle inspection that is necessary to ensure defect free masks. However, it is noted that for the leading edge lithography manufacturing, zebra features are the best option if a quality CPL zebra mask is deliverable.

In view of the foregoing, it is therefore desirable to have a CPL mask that can minimize the use of zebra patterns for imaging Zone2features, but which can still achieve the satisfactorily printing performance. Moreover, due to the variety of IC design styles, such as memory core vs. periphery pattern area, it is desirable to have a more flexible and improved CPL mask design that satisfies the printing performance required without necessarily resorting to the use of the zebra mask design for imaging, for example, Zone2features.

Thus, it is an object of the present invention to provide an alternative to the zebra patterning technique previously disclosed in the '539 reference, so as to provide a CPL mask which eliminates the foregoing issues associated with utilizing the zebra patterning technique.

SUMMARY OF THE INVENTION

As noted above, it is one object of the present invention to provide a method and technique for generating mask patterns capable of imaging features having critical dimensions corresponding to, for example, Zone1or Zone2features, that eliminates the need for the use of the zebra patterning technique.

More specifically, in one exemplary embodiment, the present invention relates to a method of generating a mask for printing a pattern including a plurality of features. The method includes the steps of obtaining data representing the plurality of features; and forming at least one of the plurality of features by etching a substrate to form a mesa and depositing a chrome layer over the entire upper surface of the mesa, where said mesa has a predetermined height.

In a second exemplary embodiment, the present invention relates to method of a generating a mask for printing a pattern comprising a plurality of features, which includes the steps of obtaining data representing the plurality of features; and forming at least one of the plurality of features by etching a substrate to form a mesa and depositing a light transmissive, phase shifting material over the entire upper surface of the mesa, where the mesa has a predetermined height.

The present invention provides important advantages over the prior art. Most importantly, the present invention eliminates the need to implement the zebra patterning technique, and significantly reduces the complexity of mask making process. In addition, the present invention provides a simple process for tuning features located, for example, in a peripheral area of the circuit design to features located in a core, dense area of the circuit design, so as to allow the peripheral located features and the core features to be imaged utilizing a single illumination. Another advantage of the present invention is that it minimizes the issues associated with phase edge printing in transition regions within the circuit design. Yet another advantage of the present invention is that by using “leaky chrome” as detailed below, it is possible to utilize both 6% attCPL and pure phase CPL features on the mask, which allows for 6% π-phase shifted light to be utilized in conjunction with features, including Zone2and Zone3features, thereby providing for improved imaging performance.

Additional advantages of the present invention will become apparent to those skilled in the art from the following detailed description of exemplary embodiments of the present invention.

The invention itself, together with further objects and advantages, can be better understood by reference to the following detailed description and the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION

As explained in more detail below, the mask and method for generating a mask in accordance with the present invention implements features utilizing a phase mesa having chrome or MoSi deposited along the entire upper surface of the features, thereby eliminating the need for formation of the zebra pattern required by the prior art zebra technique. This mask formation technique is particularly applicable to those features having a CD dimension corresponding to a Zone2feature (i.e., those features for which when the feature is implemented in the mask utilizing adjacent phase edges, the two phase-edges partially interact, but the interaction is insufficient to satisfactory image the feature). However, the technique can also be utilized to implement features falling outside of the Zone2category, such as Zone1and Zone3type features.

As shown inFIG. 2a,the CPL mask feature is 3D in nature. In other words, the CPL mask topography includes etched phase features24with and without a layer thickness of chrome22deposited on the top of the features24. It has been found that the use of 3D mask features enhance the resulting image. This is shown inFIGS. 3a-3d.FIG. 3aillustrates a CPL line feature30to be imaged, having OPC scattering bars32disposed on each side of the CPL line feature30. The cutline inFIG. 3asamples the aerial image for both SB features32and the CPL feature line30.FIG. 3billustrates a 3D mask topology in which the SB features32have a layer of chrome36deposited on the entire upper surface thereof. A 2D mask topology for the mask shown inFIG. 3awould be the same as that shown inFIG. 3b,with the difference being that there would be no chrome deposited on the top of the SB features32.FIGS. 3cand3dillustrate the resulting aerial image for the 2D topology and the 3D topology, respectively. As is shown by a comparison ofFIGS. 3cand3d,the resulting aerial image is more enhanced by the 3D mask topography as compared to the aerial image based on the 2D topology. For the CPL feature line30(phase only) of the given example, the actual I-min is approaching 0.25 for the 3D mask topology vs. 0.35 for the 2D mask topology. With respect to the SB features32, the SB features32appear much more pronounced and “darker” for the 3D mask topology vs. the 2D mask topology.

FromFIGS. 3cand3d,it is clear that the aerial image for the SB features32as influenced by 3D mask topography have more contrast than the SB features as influenced by the 2D mask topology. As such, the 3D mask topology effect makes it harder for the SB features32to maintain “sub-resolution”. It is this 3D mask topology effect that the present invention utilizes to enhance the printing performance of CPL mask features, without resorting to the need for utilizing the zebra patterning technique.

In accordance with the present invention, in a first embodiment, the CPL feature to be imaged is formed in the mask utilizing a chrome-on-mesa phase feature. More specifically, a chrome layer is deposited over the entire upper surface of a mesa phase feature etched in the substrate. As explained in further detail below, the chrome layer does not provide for light transmission and therefore does not introduce any phase-shift into the light. As best understood by the Applicants, the enhanced imaging effect results from a waveguide-effect in which the illuminated light first picks up imaging information as the light passes the sidewalls of the phase mesa and is pulled into the quartz, and then additional imaging information is picked up as this light, which was pulled into the sidewalls of the phase mesa formed in the quartz, is then blocked by the chrome deposited on top of the phase mesa (in the imaging process, the illumination light will first contact the quartz substrate, then the phase mesa etched in the substrate etch substrate and then the chrome layer deposited on top of the phase mesa). As noted, in the given embodiment, the chrome layer deposited on top of the phase mesa does not provide for transmission of light, and therefore does not introduce any phase-shift with regard to the transmitted light. The image enhancement obtained is a result of the use of the chrome-on-phase mesa structure.

FIGS. 4aand4billustrate two variations of the first embodiment of the present invention. More specifically,FIG. 4aillustrates a cross-section of a CPL mask feature which includes a quartz substrate40having a π-phase mesa42etched therein, and a chrome layer44deposited on top of the π-phase mesa42. It is noted that the chrome layer44is formed over the entire top surface of the phase mesa42(thereby eliminating the issues for fabricating the zebra pattern of the prior art).FIG. 4billustrates a cross-section of a CPL mask feature which includes a quartz substrate40having a 2π-phase mesa46etched therein, and a chrome layer44deposited on top of the 2π-phase mesa46. Once again, it is noted that the chrome layer is formed over the entire top surface of the phase mesa46.FIG. 4cillustrates a prior art mask feature in which a chrome layer47is deposited directly on the surface of the quartz substrate40.

FIG. 4dillustrates the aerial performance associated with the CPL features illustrated inFIGS. 4a-4c.It is noted that the exemplary features illustrated inFIGS. 4a-4ccorrespond to a 80 nm line feature with 360 nm pitch imaged under the exposure conditions of 0.8 NA and a quasar illumination of 0.85/0.55 setting. As shown inFIG. 4d,the aerial image43resulting from the chrome on π-phase mesa structure ofFIG. 4a,and the aerial image45resulting from the chrome on 2π-phase mesa structure ofFIG. 4bare essentially identical, and have lower (i.e., “darker”) I-min values than the aerial image47resulting from the non phase-shifted, chrome on quartz feature, ofFIG. 4c.As is known, lower I-min values result in better imaging performance for printing lines.FIG. 4dalso shows that the aerial image width is wider for the chrome on phase mesa structures. However, this can be compensated for by applying appropriate OPC techniques.

As noted, there is no noticeable aerial image performance difference between the chrome on π-phase mesa structure ofFIG. 4a,and the chrome on 2π-phase mesa structure ofFIG. 4b.However, one advantage for using the 2π-phase mesa is that it allows more tolerance since the etched range is twice as great. It is further noted that with regard to the chrome-on-mesa structure, as the chrome does not transmit light and there is no phase-shift associated with the light, it is possible to etch the substrate to heights other than corresponding to π or 2π phase shifts. The structure of the first embodiment of the present invention is particularly useful for implementing Zone2features, as defined above, in a mask design. Thus, when performing CPL full-chip treatment, and classifying the features to be imaged into either Zone1, Zone2or Zone3categories, the foregoing chrome-on-mesa phase features discussed above can be utilized to implement the Zone2features in the mask design, thereby eliminating the need to perform the zebra technique for Zone2features. As noted, the chrome is deposited over the entire upper surface of each of the Zone2features.

In a second embodiment of the present invention, as opposed to a chrome layer being deposited over the entire surface of the phase mesa etched in the substrate, a material having a certain percentage transmission is deposited over the entire upper surface of the phase mesa. For example, a layer of MoSi, which exhibits a 6% transmission of light, can be deposited over the phase mesa in order to implement the CPL feature in the mask design. It is noted that the present invention is not limited to the use of MoSi, or materials having 6% transmission, other materials and different % transmission of light may also be utilized. As with the first embodiment of the present invention, the combination of the MoSi layer and the phase mesa function to enhance the resulting imaging performance due to the waveguide effects noted above. Further, the light transmissive layer may also introduce a phase shift with respect to the transmitted light. As with the first embodiment, the second embodiment of the present invention may also be utilized to implement Zone2features in a mask design. In addition to the use of MoSi, other possible materials include, but are not limited to TaSi, CrON and Al). With respect to the transmission of light, the useful range is typically approximately 5-30%.

In addition, the structure of the second embodiment of the present invention having a light transmissive layer deposited over the entire phase mesa structure can be utilized to assist matching the exposure energy required for exposing a core portion of a circuit design with features (e.g., Zone1or Zone2type feature) disposed on a periphery of the circuit design. For example, considering a memory device, the core area of the memory device can be optimized with existing mask processes, such as 6% attPSM. This is due to the fact that 6% attPSM performs well for very dense areas under aggressive k1 (i.e., <0.31). Thus, for a very dense memory core is a preferable to utilize 6% attPSM to implement the dense core features in the mask. However, for a less dense periphery (not memory core) pattern area, the imaging performance for 6% attPSM is poor. As such, CPL techniques are a preferred option.

However, when attempting to match 6% attPSM in the core to a 100% transmission CPL feature, such as a Zone1feature, located in the periphery area, there is likely to be a mis-match in the exposure energy required to illuminate each area. Indeed, the optimum exposure energy is much different for 6% attPSM as compared to the one for optimal printing of a Zone1CPL feature. Thus, in order to ensure that both the core and the periphery print within the specified error tolerances for the given mask, it is necessary to tune the % transmission of the CPL mask feature for imaging the feature in the periphery area. One method for tuning the % transmission of the features in the periphery area is to use prior art zebra technique to implement the CPL mask features, where the size of the chrome patch and open areas can be adjusted accordingly to accomplish transmission tuning. However, this can be undesirable due to the complexity and potential difficulties associated with implementing the zebra patterning technique.

An alternative to the zebra technique is to utilize the transmissive layer on phase mesa structure of the second embodiment of the present invention.FIG. 5aillustrates how the transmissive layer on phase mesa structure can be utilized to perform the foregoing tuning, as well as illustrating the basic structure of the transmissive layer of phase mesa structure in accordance with the second embodiment. Referring toFIG. 5a,the figure illustrates a core area51of a mask design and a peripheral area52of the mask design. In the given example, the core area51includes dense features which are implemented utilizing 6% attPSM material53disposed on the substrate50. The peripheral area52includes a Zone1feature, which is implemented using the structure of the second embodiment. Specifically, the Zone1feature57is implemented by forming/etching a 2π-phase mesa54in the substrate50and then depositing a layer55of MoSi over the entire upper surface of the 2π-phase mesa54. It is noted that because the MoSi already has a π-shift, it is necessary to use 2π-etched depth for the phase mesa54. This is necessary to preserve the same phase-shift through both the 6% attPSM features53and the MoSi layer55on phase mesa feature57formed in the peripheral area. However, it is also noted that because of the 2π etch depth of the phase mesa feature54, the single phase edge59formed in the transition area between the core and peripheral area does not print because it is not phase shifted. Thus, the MoSi layer55on phase mesa structure54allows for both transmission tuning between the core and peripheral areas so that a single illumination can be utilized to image both areas, and for the prevention of imaging of single phase edges in the transition areas.

FIG. 5billustrates an example of utilizing the prior art Zone1CPL technique, in which two adjacent phase edges are utilized to image the peripheral feature. As shown, the phase edges are formed by etching the substrate to a depth of π. As discussed above, this results in the transition area having an etch depth of π, which may result in the unwanted imaging of the phase-edge in the substrate.

Thus, using 6% attPSM in core and with CPL or zebra CPL in periphery, can cause single-phase edge printing in the transition area. However, the MoSi-on-phase-mesa structure of the second embodiment has a 2π etch depth, and therefore it is not phase-shifted. As a result, it is possible to minimize single-phase edge printing issue (2π edge is not printable) in the transition from core to the periphery area. The aerial image simulation illustrated inFIG. 5cconfirms that the MoSi-on-phase mesa structure of the second embodiment has comparable imaging performance to the 6% attPSM features.

In a variation of the second embodiment, it is possible to utilize “leaky” chrome disposed on the entire upper surface of a CPL feature as shown, for example, inFIG. 6a.Similar toFIG. 5a,FIG. 6aillustrates a core portion of the circuit implemented in the mask using 6% attPSM features, and a peripheral portion in which a CPL feature utilizing the “leaky” chrome structure of the given embodiment is implemented. “Leaky” chrome as referred to herein, is chrome which is designed to allow a specific % amount of transmission of light, but has zero phase shift. This can be accomplished by, for example, but not limited to, controlling the composition of the chrome or the thickness of the chrome layer deposited on top of the CPL feature. Referring toFIG. 6a,the CPL feature60, which may be for example a Zone1or Zone2type feature has a layer of “leaky” chrome62deposited on the entire upper surface of the feature. By etching the background area adjacent the CPL feature having the leaky chrome deposited thereon to a π etch depth, it is possible to utilize this structure to create “effective PSM”, because the light passing through the background area is π-phase shifted relative to the light passing through the leaky chrome. Thus, the CPL feature with leaky chrome disposed thereon provides for effective PSM with controllable transmission and therefore can also be utilized to tune the features in a peripheral area of a mask design such that the features in a core area and the features in the peripheral area can be imaged within acceptable error criteria with a single illumination.

As another example, the chrome is deposited over substantially the entire upper surface of the CPL feature and has a thickness sufficiently thin such that the chrome exhibits substantially 6% transmission. The 6% transmission chrome in combination with the etched substrate, which is etch to a π-phase depth, form the Zone2feature in the mask. By utilizing the foregoing technique, the mask making process is significantly reduced as there is no longer a need for a plurality of chrome strips to be utilized in conjunction with each Zone2feature. It is also possible to utilize the leaky chrome on Zone3features.

In another variation as shown inFIG. 6b,in addition to the CPL feature60being formed with leaky chrome, the leaky chrome may also be utilized to form the core area features. Referring toFIG. 6b,leaky chrome62is deposited over the substrate50in replacement of the attenuated PSM material53shown inFIG. 6aso as to form the dense features in the core area of the mask pattern. It is noted, however, that it would also be necessary to etch the background portion of the substrate to a π-phase etch depth in the core area if leaky chrome is to be utilized to image the core area features.

As noted above, the present invention provides important advantages over the prior art. Most importantly, the present invention eliminates the need to implement the zebra patterning technique, and significantly reduces the complexity of mask making process. In addition, the present invention provides a simple process for tuning features located, for example, in a peripheral area of the circuit design to features located in a core, dense area of the circuit design, so as to allow the peripheral located features and the core features to be imaged utilizing a single illumination. Yet another advantage of the present invention is that it minimizes the issues associated with phase edge printing in transition regions within the circuit design.

Computer system100may be coupled via bus102to a display112, such as a cathode ray tube (CRT) or flat panel or touch panel display for displaying information to a computer user. An input device114, including alphanumeric and other keys, is coupled to bus102for communicating information and command selections to processor104. Another type of user input device is cursor control116, such as a mouse, a trackball, or cursor direction keys for communicating direction information and command selections to processor104and for controlling cursor movement on display112. This input device typically has two degrees of freedom in two axes, a first axis (e.g., x) and a second axis (e.g., y), that allows the device to specify positions in a plane. A touch panel (screen) display may also be used as an input device.

According to one embodiment of the invention, the coloring process may be performed by computer system100in response to processor104executing one or more sequences of one or more instructions contained in main memory106. Such instructions may be read into main memory106from another computer-readable medium, such as storage device110. Execution of the sequences of instructions contained in main memory106causes processor104to perform the process steps described herein. One or more processors in a multi-processing arrangement may also be employed to execute the sequences of instructions contained in main memory106. In alternative embodiments, hard-wired circuitry may be used in place of or in combination with software instructions to implement the invention. Thus, embodiments of the invention are not limited to any specific combination of hardware circuitry and software.

Computer system100can send messages and receive data, including program code, through the network(s), network link120, and communication interface118. In the Internet example, a server130might transmit a requested code for an application program through Internet128, ISP126, local network122and communication interface118. In accordance with the invention, one such downloaded application provides for the illumination optimization of the embodiment, for example. The received code may be executed by processor104as it is received, and/or stored in storage device110, or other non-volatile storage for later execution. In this manner, computer system100may obtain application code in the form of a carrier wave.

FIG. 8schematically depicts a lithographic projection apparatus suitable for use with a mask designed with the aid of the current invention. The apparatus comprises:a radiation system Ex, IL, for supplying a projection beam PB of radiation. In this particular case, the radiation system also comprises a radiation source LA;a first object table (mask table) MT provided with a mask holder for holding a mask MA (e.g., a reticle), and connected to first positioning means for accurately positioning the mask with respect to item PL;a second object table (substrate table) WT provided with a substrate holder for holding a substrate W (e.g., a resist-coated silicon wafer), and connected to second positioning means for accurately positioning the substrate with respect to item PL;a projection system (“lens”) PL (e.g., a refractive, catoptric or catadioptric optical system) for imaging an irradiated portion of the mask MA onto a target portion C (e.g., comprising one or more dies) of the substrate W.

As depicted herein, the apparatus is of a transmissive type (i.e., has a transmissive mask). However, in general, it may also be of a reflective type, for example (with a reflective mask). Alternatively, the apparatus may employ another kind of patterning means as an alternative to the use of a mask; examples include a programmable mirror array or LCD matrix.

The source LA (e.g., a mercury lamp or excimer laser) produces a beam of radiation. This beam is fed into an illumination system (illuminator) IL, either directly or after having traversed conditioning means, such as a beam expander Ex, for example. The illuminator IL may comprise adjusting means AM for setting the outer and/or inner radial extent (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution in the beam. In addition, it will generally comprise various other components, such as an integrator IN and a condenser CO. In this way, the beam PB impinging on the mask MA has a desired uniformity and intensity distribution in its cross-section.

It should be noted with regard toFIG. 8that the source LA may be within the housing of the lithographic projection apparatus (as is often the case when the source LA is a mercury lamp, for example), but that it may also be remote from the lithographic projection apparatus, the radiation beam that it produces being led into the apparatus (e.g., with the aid of suitable directing mirrors); this latter scenario is often the case when the source LA is an excimer laser (e.g., based on KrF, ArF or F2lasing). The current invention encompasses both of these scenarios.

The depicted tool can be used in two different modes:In step mode, the mask table MT is kept essentially stationary, and an entire mask image is projected in one go (i.e., a single “flash”) onto a target portion C. The substrate table WT is then shifted in the x and/or y directions so that a different target portion C can be irradiated by the beam PB;In scan mode, essentially the same scenario applies, except that a given target portion C is not exposed in a single “flash”. Instead, the mask table MT is movable in a given direction (the so-called “scan direction”, e.g., the y direction) with a speed v, so that the projection beam PB is caused to scan over a mask image; concurrently, the substrate table WT is simultaneously moved in the same or opposite direction at a speed V=Mv, in which M is the magnification of the lens PL (typically, M=¼ or ⅕). In this manner, a relatively large target portion C can be exposed, without having to compromise on resolution.

Additionally, software may implement or aid in performing the disclosed concepts. Software functionalities of a computer system involve programming, including executable code, may be used to implement the above described imaging model. The software code is executable by the general-purpose computer. In operation, the code, and possibly the associated data records, are stored within a general-purpose computer platform. At other times, however, the software may be stored at other locations and/or transported for loading into the appropriate general-purpose computer systems. Hence, the embodiments discussed above involve one or more software products in the form of one or more modules of code carried by at least one machine-readable medium. Execution of such code by a processor of the computer system enables the platform to implement the catalog and/or software downloading functions in essentially the manner performed in the embodiments discussed and illustrated herein.

As used herein, terms such as computer or machine “readable medium” refer to any medium that participates in providing instructions to a processor for execution. Such a medium may take many forms, including but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical or magnetic disks, such as any of the storage devices in any computer(s) operating as one of the server platforms discussed above. Volatile media include dynamic memory, such as main memory of such a computer platform. Physical transmission media include coaxial cables, copper wire and fiber optics, including the wires that comprise a bus within a computer system. Carrier-wave transmission media can take the form of electric or electromagnetic signals, or acoustic or light waves such as those generated during radio frequency (RF) and infrared (IR) data communications. Common forms of computer-readable media therefore include, for example: a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD, any other optical medium, less commonly used media such as punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wave transporting data or instructions, cables or links transporting such a carrier wave, or any other medium from which a computer can read programming code and/or data. Many of these forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to a processor for execution.