KR20070019618A - An improved ??? mask and a method and program product for generating the same - Google Patents

Abstract

The present invention relates to a method of generating a mask for printing a pattern comprising a plurality of features. The method includes obtaining data indicative of a plurality of features; And forming at least one of the plurality of features to be formed by etching the substrate to form a mesa, and depositing a chromium layer over the entire top surface of the mesa, wherein the mesa has a predetermined height.

Description

Improved CPU masks and programs and methods for generating the masks {AN IMPROVED CCL MASK AND A METHOD AND PROGRAM PRODUCT FOR GENERATING THE SAME}

1A-1C illustrate known techniques for implementing features having different CD dimensions using a CPL mask and corresponding imaging capabilities of each technique;

2A illustrates a known CPL mask for imaging three parallel lines using the CPL zebra technique to image features and corresponding imaging performance of the mask;

FIG. 2B illustrates a standard Alt-PSM mask design that images the same three line features as the mask shown in FIG. 2A and the corresponding imaging performance of the mask;

3A illustrates an example CPL line feature with scattering bars adjacent to each edge;

FIG. 3B illustrates a 3D mask topology with the SB features of FIG. 3A having a chromium layer deposited on its entire top surface; FIG.

3C and 3D illustrate the resulting aerial image for 2D and 3D topologies, respectively;

4A is a cross-sectional view of a CPL mask feature in accordance with the present invention implemented using a chromium layer deposited over a π-phase mesa etched in a substrate;

4B is a cross-sectional view of a CPL mask feature in accordance with the present invention implemented using a chromium layer deposited over a 2π-phase mesa etched in a substrate;

4C is a cross-sectional view of a prior art binary mask feature in accordance with the present invention implemented using a chromium layer deposited on a substrate;

4D illustrates aerial image performance associated with the CPL and binary features illustrated in FIGS. 4A-4C;

FIG. 5A illustrates a CPL mask feature formed in accordance with the second embodiment and disposed within the peripheral area of a circuit having a core portion implemented with 5% AttPSM; FIG.

5B illustrates a prior art implementation of a mask with 6% AttPSM and binary features;

5C illustrates the aerial image performance of the CPL mask feature of FIG. 5A for features in the core portion of the circuit implemented using 6% AttPSM.

FIG. 6A illustrates a variation of the second embodiment where the CPL feature is implemented using a “leaky” chrome structure; FIG.

FIG. 6B illustrates another variant of the second embodiment in which the features in the core region are also formed using “Licky” chromium; FIG.

7 is a block diagram illustrating a computer system capable of implementing lighting optimization in accordance with one embodiment of the present invention;

8 is a schematic illustration of an exemplary lithographic projection apparatus suitable for use with a mask designed with the aid of the disclosed concepts.

This application claims priority to US patent application Ser. No. 60 / 707,557, filed August 12, 2005, which is incorporated by reference in its entirety.

FIELD OF THE INVENTION The present invention generally relates to the generation of mask patterns for use with chromeless phase lithography (CPL) techniques, and more particularly to improving the imaging of critical features, while at the same time A technique and method for reducing the complexity of a mask fabrication process required to create a mask capable of imaging a feature.

Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, the mask may comprise a circuit pattern corresponding to an individual layer of the IC, which pattern may include (eg, one or more dies) on a substrate (silicon wafer) coated with a layer of radiation sensitive material (resist). ) Onto the target portion. In general, a single wafer will contain an entire network of adjacent target portions that are irradiated one at a time through the projection system. In one type of lithographic projection apparatus, each target portion is irradiated by exposing the entire mask pattern onto the target portion at once; Such a device is commonly referred to as a wafer stepper. In an alternative apparatus, commonly referred to as a step-and-scan apparatus, the mask pattern is progressively scanned in a given reference direction ("scanning" direction) under the projection beam, parallel to this direction ( Each target portion is irradiated by synchronously scanning the substrate table in parallel in the same direction or anti-parallel (parallel in the opposite direction). Since the projection system generally has a magnification factor M (generally <1), the speed at which the substrate table is scanned will be a factor M of the speed at which the mask table is scanned. More information relating to lithographic devices as described herein can be obtained, for example, from US Pat. No. 6,046,792, which is incorporated herein by reference.

In a manufacturing process using a lithographic projection apparatus, a mask pattern is imaged on a substrate, wholly or partially applied by a layer of radiation sensitive material (resist). Prior to this imaging step, the substrate may be subjected to various processes such as priming, resist coating and soft bake. After exposure, the substrate may undergo other processes such as post-exposure bake (PEB), development, hard bake, and measurement / inspection of imaged features. This series of procedures is used as the basis for patterning individual layers of devices, such as ICs. This patterned layer can then go through various processes, such as etching, ion-implantation (doping), metallization, oxidation, chemical-mechanical polishing, etc., all of which are intended to finish the individual layers. If several layers are required, the whole process or variations thereof will have to be repeated for each new layer. Eventually, an array of devices will be present on the substrate (wafer). The devices are then separated from each other by techniques such as dicing or sawing, and the individual devices can be mounted on a carrier and connected to pins or the like.

For simplicity, the projection system may hereinafter be referred to as the "lens"; However, the term should be broadly interpreted as encompassing various types of projection systems including, for example, refractive optics, reflective optics and catadioptric systems. The radiation system may also include components that operate according to any of the types of design for directing, shaping or controlling the projection beam of radiation, which components may be referred to collectively or individually as "lenses". Can be. Further, the lithographic apparatus may be of a type having two or more substrate tables (and / or two or more mask tables). In such "multiple stage" devices additional tables may be used in parallel, or preparatory steps may be carried out on one or more tables while one or more other tables are being used for exposure. Twin stage lithographic apparatus are disclosed, for example, in US Pat. No. 5,969,441, which is incorporated herein by reference.

The above-mentioned photolithography mask includes geometric patterns corresponding to the circuit components to be integrated onto the silicon wafer. The patterns used to create such masks can be generated using computer-aided design (CAD) programs, which is often referred to as electronic design automation (EDA). Most CAD programs follow a set of preset design rules for generating functional masks. These rules are set by processing and design constraints. For example, design rules define a space tolerance between circuit devices (eg, gates, capacitors, etc.) or interconnect lines, such that the circuit devices or lines are mutually interconnected in an undesired manner. To ensure that it does not work. Design rule restrictions are also commonly referred to as "critical dimensions" (CDs). The critical dimension of the circuit can be defined as the minimum width of one line or the minimum spacing between two lines. Thus, the CD determines the overall size and density of the designed circuit.

Of course, one of the purposes of integrated circuit fabrication is to faithfully reproduce the original circuit design on the wafer (via the mask). In order to further improve the resolution / printing capability of photolithography equipment, one technique that is currently in the spotlight from the photolithography community is referred to as chromeless phase lithography "CPL." As is known, when using CPL technology, the resulting mask pattern typically uses chromium as well as a structure (corresponding to the features to be printed on the wafer) that does not require the use of chromium (in other words, the features are phased). Printed by the shift technique). Such CPL masks are disclosed in USP Publication No. 2004-0115539 ('539 Reference), which is incorporated herein by reference in its entirety.

As described in the '539 reference above, it has been found beneficial to classify mask design features into "three zones" for practical manufacturing purposes. Referring to FIG. 1A, Zone 1 features are features having critical dimensions within a range in which two phase edges (left and right) interact closely and form a single aerial image. Since the two phase edges fall further (or larger feature CDs), each of the left and right phase edges forms its own aerial image and the two do not interact as shown in FIG. 1C. This type of feature is classified as Zone 3. In this case, to prevent the Zone 3 features from being printed in two separate line patterns, a piece of dark chromium is placed on top of the substrate, and the Zone 3 features form a single aerial image as shown in FIG. 1C. do. In other words, Zone 3 features are essentially "chrome" mask features.

If the two phase-edges are CD dimensioned to partially interact as shown in FIG. 1B, these features are classified as Zone 2 features. However, aerial images formed by partial phase edge interaction are very poor in quality and therefore cannot be used. The '539 reference discloses that high fidelity aerial images for these features can be obtained by tuning the percent transmission using chrome patches. Thus, by classifying randomly designed mask features into three imaging zones, and then applying optical proximity correction, it is possible to achieve volume IC fabrication with a CPL mask.

2A and 2B illustrate the application of a chrome patch (also called a "zebra" technique) and the application of a standard alternating phase-shift mask (Alt-PSM), respectively, and also of Alt-PSM technique and CPL zebra technique. Illustrate the comparison between performances. With reference to FIG. 2A, for Zone 2 features (which are three parallel lines in the given example), the quartz substrate 20 is etched to form three sets of adjacent π-phase edges, and then the etched feature A chrome patch 22 is disposed on top of the features 24 formed by etching to form a strip / patch of chrome (ie, zebra pattern) on the top surface of the 24. The duty ratio of the "zebra" pattern needs to be un-resolvable by the imaging tool such that the "zebra" is essentially digitally halftone. In other words, Zone 2 features are "shaded" phase patterns from the perspective of the image tool. The amount of shading (ie percent transmission) is determined by the ratio between the size of the chrome patch (dark) to the size of the open area (bright). By using such patches, one can control the percent transmission for Zone 2 mask features and achieve high quality patterning.

Indeed, as shown in FIG. 2A, the “zebra” features are comfortably rival with the imaging performance associated with the standard alternating PSM (AltPSM) mask 26 illustrated in FIG. 2B and imaged by the mask of FIG. 2A. The same three parallel line patterns are imaged as follows. As shown, the two resulting aerial images represent a good minimum aerial image (I-min), since lower I-min means a "darker" image that can form a higher quality line pattern better. It exhibits better image contrast. However, for Zone 2 features imaged using 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 advantages of using the Zebra CPL techniques because more viable OPC processing is feasible. One issue associated with using zebra technology to implement zone 2 features in a mask is that such zebra mask features require the use of an e-beam or high-resolution mask fabrication process. Borderline quality zebra mask patterns reduce the effectiveness of transmittance control during patterning. In addition, the zebra pattern can cause the difficulty of reticle inspection, which is essential for ensuring flawless masks. However, for leading edge lithography manufacturing, zebra features are the best choice if a good quality CPL zebra mask is deliverable.

Therefore, from the previous point of view, it is desirable to have a CPL mask that can still achieve satisfactory printing performance while minimizing the use of zebra patterns to image zone 2 features. Moreover, due to the diversity of IC design styles, such as memory core vs. peripheral pattern areas, printing performance required without resorting to the use of zebra mask designs for imaging zone 2 features, for example. It is desirable to have improved CPL mask design and more flexibility to meet the requirements.

It is therefore an object of the present invention to provide an alternative to the zebra patterning technique disclosed in the '539 reference above, to provide a CPL mask that eliminates previous issues associated with using the zebra pattern technique.

As described above, one object of the present invention is to create a mask pattern capable of imaging features having critical dimensions corresponding to, for example, Zone 1 or Zone 2 features, which eliminates the need for the use of zebra patterning techniques. It is to provide a technique and method.

More specifically, in one exemplary embodiment the invention relates to a method of generating a mask for printing a pattern comprising a plurality of features. The method includes obtaining data indicative of a plurality of features; And forming at least one of the plurality of features by etching the substrate to form a mesa and depositing a chromium layer over the entire top surface of the mesa, wherein the mesa has a predetermined height.

In a second exemplary embodiment the present invention relates to a method of generating a mask for printing a pattern comprising a plurality of features, the method comprising: obtaining data indicative of 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 top surface of the mesa, wherein the mesa has a predetermined height.

The present invention provides significant advantages over the prior art. Most importantly, the present invention eliminates the need to implement zebra patterning techniques and significantly reduces the complexity of the mask fabrication process. In addition, the present invention provides a simple process for adjusting features located in the peripheral area of the circuit design, for example, in the dense area of the circuit design, for features located in the core. To allow peripherally located features and core features to be imaged using 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. Another advantage of the present invention is to allow 6% π-phase shifted light to be used in conjunction with features including Zone 2 and Zone 3 features by using "leaky chrome" as described below. Both 6% attCPL and pure phase CPL features on the mask can be used to provide improved imaging performance.

Those skilled in the art will recognize further advantages of the present invention from the following detailed description of exemplary embodiments of the present invention.

While reference is made herein to specific uses in the manufacture of ICs, it should be clearly understood that the present invention has many other possible applications. For example, it can be employed in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, liquid crystal displays (LCDs), thin film magnetic heads. Those skilled in the art, with respect to this alternative application, use of any term such as "reticle", "wafer" or "die" as used herein, respectively, such as "mask", "substrate" or "target portion", respectively. It should be considered to be substituted with more general terms and synonyms.

The invention itself together with further objects and advantages will be more readily understood by reference to the accompanying drawings and the following detailed description.

As described in more detail below, the method and mask generation method according to the present invention implements features using phase mesas with chromium or MoSi deposited along the entire upper surface of the features, thereby providing a Eliminates the need for the formation of zebra patterns required by This masking technique uses features with CD dimensions corresponding to zone 2 features (when the feature is implemented within the mask using adjacent phase edges, the two phase-edges partially interact, but the interactions cause the feature to Inadequate features to image satisfactorily). However, the technique can also be used to implement features outside of the Zone 2 category, such as Zone 1 and Zone 3 type features.

As shown in FIG. 2A, the CPL mask feature is inherently 3D. In other words, CPL mask topography includes etched phase features 24 with and without layer thickness of chromium deposited on top of features 24. It has been found that the use of 3D mask features enhances the resulting image. This is illustrated in Figures 3A-3D. 3A illustrates a CPL line feature 30 to be imaged with OPC scattering bars 32 disposed on each side of the CPL line feature 30. The cutline of FIG. 3A samples the aerial image for SB features 32 and CPL feature line 30. 3B illustrates a 3D mask topology in which SB features 32 have a layer of chromium 36 deposited on its entire top surface. The 2D mask topology for the mask shown in FIG. 3A may be the same as that shown in FIG. 3B, with the difference that no chromium will be deposited on top of the SB features 32. 3C and 3D illustrate the resulting aerial image for 2D and 3D topologies, respectively. As shown in comparison to FIGS. 3C and 3D, the resulting aerial image is further enhanced by the 3D mask topology compared to the aerial image based on the 2D topology. For the given example CPL feature line 30 (phase only), the actual I-min reaches 0.25 for the 2D mask topology, while the actual I-min reaches 0.25 for the 3D mask topology. For SB features 32, the SB features 32 appear much more pronounced and appear “darker” for the 3D mask topology versus the 2D mask topology.

3C and 3D, the aerial image for SB features 32 affected by the 3D mask topology has better contrast than the SB features affected by the 2D mask topology. As such, the 3D mask topology effect makes it more difficult for SB features to maintain "sub-resolution". It is this 3D mask topology effect that the present invention uses to improve the printing performance of CPL mask features without resorting to the need to use zebra patterning techniques.

According to the present invention, the CPL features to be imaged in the first embodiment are formed in the mask using chrome-on-mesa phase features. More specifically, a chromium layer is deposited over the entire top surface of the mesa phase features etched in the substrate. As will be explained in more detail below, the chromium layer does not provide light transmittance and therefore does not introduce any phase-shift into the light. As the applicant understands best, the enhanced imaging effect first picks up imaging information as light passes through the sidewalls of the phase mesa and is pulled into the quartz, and then (sidewall of the phase mesa formed in the quartz). As the light pulled into the field is blocked by chromium deposited on top of the phase mesa, then due to the waveguide-effect (after imaging) the additional imaging information is picked up (in the imaging process, the illumination light is first quartz Phase mesas that are in contact with the substrate and then etched into the substrate etch the substrate, and then a chromium layer is deposited on top of the phase mesas). As mentioned, in a given embodiment the chromium layer deposited on top of the phase mesa does not provide a transmission of light and therefore does not introduce any phase-shift for the transmitted light. The image enhancement obtained is the result of the use of chromium-on-phase mesa structures.

4A and 4B illustrate two variants of the first embodiment of the present invention. More specifically, FIG. 4A illustrates a CPL mask feature comprising an etched π-phase mesa 42 and a quartz substrate 40 having a chromium layer 44 deposited on top of the π-phase mesa 42. Illustrative cross-sectional view of Note that the chromium layer 44 is formed on the entire top surface of the phase mesa 42 (thus eliminating issues for fabricating the zebra pattern of the prior art). 4B illustrates a cross-sectional view of a CPL mask feature including a etched 2π-phase mesa 46 and a quartz substrate 40 having a chromium layer 44 deposited on top of the 2π-phase mesa 46. . Similarly, note that a chromium layer is formed on the entire top surface of the phase mesa 46. 4C illustrates a prior art mask feature in which a chromium layer 47 is deposited directly on the surface of a quartz substrate 40.

4D illustrates the aerial performance associated with the CPL features illustrated in FIGS. 4A-4C. Note that the example features shown in FIGS. 4A-4C correspond to 80 nm line features with 360 nm pitch imaged under quasar illumination of 0.8NA / 0.55 setting and exposure conditions of 0.8NA. As shown in FIG. 4D, the aerial image 43 due to the chromium on π-phase mesa structure of FIG. 4A and the aerial image 45 due to the chrome on 2π-phase mesa structure of FIG. 4B are essentially the same. Have lower (i.e., "darker") I-min values than the aerial image 47 due to the non-phase-shifted chromium on quartz feature of FIG. As is known, lower I-min values lead to better performance for printing lines. 4D also shows that the aerial image width is wider for the chrome on phase mesa structure. However, this can be compensated by applying appropriate OPC techniques.

As shown, there is no appreciable aerial image performance difference between the chromium on π-phase mesa structure of FIG. 4A and the chromium on 2π-phase mesa structure of FIG. 4B. However, one advantage of using 2π-phase mesas is that they allow greater tolerance because the etched range is twice as large. In addition, with respect to the chromium-on-mesa structure, since the chromium does not transmit light and there is no phase-shift associated with the light, it is also possible to etch the substrate to a height other than corresponding to π or 2π phase shift. Be careful. The structure of the first embodiment of the present invention is particularly useful for implementing Zone 2 features in mask design as defined above. Thus, when performing CPL full-chip processing and classifying the features to be imaged into the Zone 1, Zone 2, or Zone 3 categories, the previous chrome-on-mesa phase features described above will be used to implement Zone 2 features in the mask design. As such, it eliminates the need to perform zebra techniques on Zone 2 features. As shown, chromium is deposited over the entire top surface of each of the Zone 2 features.

In contrast to the chromium layer being deposited over the entire surface of the phase mesa etched in the substrate, in a second embodiment of the invention a material having a percentage of transmittance is deposited over the entire top surface of the phase mesa. For example, a layer of MoSi that exhibits 6% light transmission may be deposited over the phase mesa to implement CPL features in mask design. Note that the present invention is not limited to the use of MoSi or a material having a 6% transmittance, and other materials and other% light transmittances may be used. As in the first embodiment of the present invention, the combination of the MoSi layer and the phase mesa serves to improve the resulting imaging performance due to the waveguide effects mentioned above. The light transmissive layer may also introduce a phase shift with respect to the transmitted light. Similar to the first embodiment, the second embodiment of the present invention may be used to implement Zone 2 features in mask design. In addition to the use of MoSi, other possible materials include, but are not limited to, TaSi, CrON and Al. Useful ranges for light transmittance are typically about 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 is a circuit using features (eg, Zone 1 or Zone 2 type features) disposed on the periphery of the circuit design. It can be used to help match the exposure energy required to expose the core portion of the design. For example, considering a memory device, the core region of the memory device may 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 (ie <0.31). Thus, for very dense memory cores, it is desirable to use 6% attPSM to implement dense core features in the mask. However, for less dense peripheral (not memory core) pattern regions, the imaging performance for 6% attPSM is poor. As such, CPL techniques are the preferred choice.

However, if an attempt is made to match 6% attPSM within the core for 100% transmissive CPL features located in the surrounding area, such as Zone 1 features, mis-matching of the exposure energy required to illuminate each area. It is easy to match. In practice, the optimal exposure energy is very different for 6% attPSM compared to for optimal printing of Zone 1 CPL features. Thus, to ensure that the core and periphery are printed within the error tolerance specified for a given mask, it is necessary to adjust the% transmittance of the CPL mask feature to image the feature in the periphery area. One way to adjust the% transmission of features in the peripheral area is to use conventional zebra technology to implement CPL mask features, and the size of the chrome patch and open areas can be adjusted accordingly to achieve transmission control. . However, this may be undesirable as it introduces potential problems and complexity associated with implementing the zebra pattern technique.

One alternative to the zebra technique is to use a transmissive layer on the phase mesa structure of the second embodiment of the present invention. 5A illustrates the manner in which the transmissive layer on the phase mesa structure can be used to perform the previous adjustment and the basic structure of the transmissive layer of the phase mesa structure according to the second embodiment. Referring to FIG. 5A, the figure illustrates the core region 51 of the mask design and the peripheral region 52 of the mask design. In the given example, core region 51 includes dense features implemented using 6% attPSM material 53 disposed on substrate 50. Peripheral region 52 includes Zone 1 features implemented using the structure of the second embodiment. Specifically, Zone 1 feature 57 is implemented by forming / etching a 2π-phase mesa 54 in the substrate 50 and then MoSi layer 55 over the entire top surface of the 2π-phase mesa 54. Deposit. Note that it is necessary to use a 2π-etched depth for the phase mesa 54 since the MoSi layer already has π-shift. This needs to preserve the same phase-shift through the MoSi layer 55 on the 6% attPSM features 53 and the phase mesa feature 57 formed in the peripheral region. However, note that due to the 2π etch depth of the phase mesa feature 54, the single phase edge 59 formed in the transition region between the core and the peripheral region is not printed because it is not phase shifted. Thus, the MoSi layer 55 on the phase mesa structure 54 allows both transmission adjustment between the core and the peripheral region and prevention of imaging of single phase edges in the transition regions so that a single illumination can be used to image the two regions. do.

5B shows an example using conventional Zone 1 CPL techniques in which two adjacent phase edges are used to image peripheral features. As shown, the phase edges are formed by etching the substrate to a depth of π. As mentioned above, this leads to a transition region with an etch depth of π, which can lead to unwanted imaging of phase-edges in the substrate.

Thus, using 6% attPSM in the core and CPL or zebra CPL around can lead to single-phase edge printing in the transition region. However, the MoSi-on-phase-mesa structure of the second embodiment has a 2π etch depth and is therefore not phase-shifted. As a result, single-phase edge printing issues can be minimized upon transition from the core to the surrounding area (2π edges cannot be printed). The aerial image simulation illustrated in FIG. 5C confirms that the MoSi-on-phase-mesa structure of the second embodiment has imaging performance comparable with 6% attPSM features.

In a variant of the second embodiment, it is possible to use "Ricky" chromium disposed on the entire upper surface of the CPL feature, for example as shown in Figure 6A. Similar to FIG. 5A, FIG. 6A illustrates the core portion of the circuit implemented in the mask using 6% attPSM features and the peripheral area in which the “Licky” chrome structure of a given embodiment is implemented. "Licky" chromium as referred to herein is chromium that is designed to allow a certain percentage amount of light transmission but with a phase shift of zero. This may be achieved, for example, but not limited to, by controlling the composition of the chromium or the thickness of the chromium layer deposited on top of the CPL feature. Referring to FIG. 6A, a CPL feature 60, which may be a Zone 1 or Zone 2 type feature, for example, has a layer of “Licky” chrome 62 deposited on the entire top surface of the feature. By etching the background region adjacent to the CPL feature having Ricky chromium deposited to π etch depth, to produce an "effective PSM" because the light passing through the background region is π-phase shifted with respect to the light passing through Ricky chromium. This structure can be used. Thus, the CPL feature with Ricky Chromium disposed provides an effective PSM with controllable transmission, so that features in the core region and features in the peripheral region can be imaged within acceptable error criteria with a single illumination. It can be used to adjust features within the peripheral area of the mask design.

In another example, chromium is deposited over substantially the entire top surface of the CPL feature and has a relatively thin thickness such that chromium exhibits a substantially 6% transmission. The 6% transmittance chromium in combination with the etched substrate etched to [pi] -phase depth forms zone 2 features in the mask. Using the techniques described above, the mask fabrication process is significantly shortened because a plurality of chromium strips are no longer needed to be used in conjunction with each Zone 2 feature. In addition, Ricky chrome on Zone 3 features may be used.

In another variation, as shown in FIG. 6B, in addition to forming CPL features 60 with Ricky chromium, Ricky chromium may also be used to form core region features. Referring to FIG. 6B, Ricky Chrome 62 is deposited over the substrate 50 upon replacement of the damped PSM material 53 shown in FIG. 6A to form dense features in the core region of the mask pattern. However, if Ricky chromium should be used to image core region features, it may be necessary to etch the background portion of the substrate to the π-phase etch depth within the core region.

As mentioned, the present invention provides significant advantages over the prior art. Most importantly, the present invention eliminates the need to implement zebra patterning techniques and significantly reduces the complexity of the mask fabrication process. In addition, the present invention provides a simple process for adjusting features located in the peripheral area of the circuit design, for example, in the dense area of the circuit design, for features located within the core, thereby providing peripherally located features and core features. Allow them to be imaged using a single light. Another advantage of the present invention is that it minimizes the issues associated with phase edge printing in transition regions in circuit design.

7 is a block diagram illustrating a computer system 100 that can implement the lighting optimization described above. Computer system 100 includes a bus 102 or other communication mechanism for conveying information and a processor 104 coupled with a bus 102 for processing information. In addition, computer system 100 couples to bus 102, such as a random access memory (RAM) or other dynamic storage device that stores information and instructions to be executed by processor 104. Ring main memory 106. In addition, main memory 106 may be used to store temporary variables or other intermediate information at the time of execution of instructions to be executed by processor 104. In addition, computer system 100 includes a read only memory (ROM) 108 or other static storage device coupled to bus 102 that stores static information and instructions for processor 104. do. Storage device 110, such as a magnetic disk or an optical disk, is provided for storing information and instructions and is coupled to bus 102.

Computer system 100 is connected via bus 102 to display 112, such as a cathode ray tube (CRT) or a flat panel or touch panel display that shows information to a computer user. Can be coupled. Input device 114, including alphanumeric or other keys, is coupled to bus 102 to convey information and command selections to processor 104. Another form of user input device passes cursor information and command selections to the processor 104 and cursor controls such as a mouse, trackball or cursor direction keys that control the movement of the cursor on the display 112. 116). 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), allowing the device to describe its position in the plane. . Also, a touch panel (screen) display may be used as the input device.

According to one embodiment of the invention, a coloring process may be performed by computer system 100 in response to processor 104 executing one or more sequences of one or more instructions contained in main memory 106. Can be. Such instructions may be read into main memory 106 from another computer readable medium, such as storage device 110. Execution of the sequences of instructions contained in main memory 106 causes processor 104 to perform the process steps described herein. In addition, one or more processors in a multi-processing arrangement may be employed to execute the sequences of instructions contained in main memory 106. In alternative embodiments, hard-wired circuitry may be used in combination with or instead of software instructions that implement the present invention. Thus, embodiments of the invention are not limited to any particular combination of hardware circuitry and software.

As used herein, the term “computer readable medium” refers to any medium that participates in providing instructions to the processor 104 for execution. Such media are not limited to non-volatile media, volatile media, and transmission media, but can take many forms, including them. Non-volatile media includes, for example, optical or magnetic disks, such as storage device 110. Volatile media includes dynamic memory, such as main memory 106. Transmission media include coaxial cables, copper wires and fiber optics, including wires comprising bus 102. In addition, the transmission medium may take the form of an acoustic wave or an optical wave as generated during radio frequency (RF) and infrared (IR) data communications. Common forms of computer readable media include, for example, floppy disks, flexible disks, hard disks, magnetic tapes, any other magnetic media, CD-ROMs, DVDs, any other Optical media, punch cards, paper tapes, any other physical media using patterns of holes, RAM, PROM, EPROM, FLASH-EPROM, any other memory chip or cartridge (cartridge), the carrier wave described herein, or any other medium that can be read by a computer.

Various forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to processor 104 for execution. For example, the instructions may initially be bear on a magnetic disk of a remote computer. The remote computer can load instructions into its dynamic memory and send the instructions over a telephone line using a modem. Modem local to computer system 100 may receive data on a telephone line and may use an infrared transmitter to convert the data into an infrared signal. An infrared detector coupled to bus 102 may receive data transferred in an infrared signal and place the data on bus 102. Bus 102 transfers the data to main memory 106 where processor 104 retrieves and executes instructions. Instructions received by main memory 106 may optionally be stored in storage device 110 before or after execution by processor 104.

The computer system 100 also preferably includes a communication interface 118 coupled to the bus 102. The communication interface 118 provides two-way data communication that couples to a network link 120 that is connected to the local network 122. For example, the communication interface 118 may be a modem that provides a data communication connection in a corresponding form of an integrated services digital network (ISDN) card or telephone line. As another example, communication interface 118 may be a local area network (LAN) card that provides a data communication connection to a compatible LAN. In addition, a wireless link may be implemented. In any such implementation, communication interface 118 transmits and receives electrical, electromagnetic or optical signals that carry digital data streams representing various types of information.

Typically, network link 120 provides data communication to other data devices over one or more networks. For example, the network link 120 may be a local network 122 connected to a data device operated by a host computer 124 or an internet service provider ISP 126. It can provide a connection through. As a result, ISP 126 provides data communication services via a worldwide packet data communication network, commonly referred to herein as " Internet 128 ". Local network 122 and the Internet 128 use electrical, electromagnetic or optical signals that carry digital data streams. Signals over various networks and signals on network link 120 through communication interface 118 that communicate digital data to and from computer system 100 are exemplary forms of carriers for conveying information.

Computer system 100 may transmit messages and receive data including program code via network (s), network link 120 and communication interface 118. In the Internet example, server 130 may send the required code for the application via the Internet 128, ISP 126, local network 122, and communication interface 118. According to the invention, for example, this downloaded application provides for the lighting optimization of the embodiment. The received code may be executed by the processor 104 as it is received and / or stored in the storage device 110 or other non-volatile storage for later execution. In this manner, computer system 100 may obtain application code in the form of a carrier wave.

8 schematically depicts a lithographic projection apparatus suitable for use with a mask designed with the aid of the present invention. The device is:

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 supporting a mask MA (e.g. a reticle) and connected to first positioning means for accurately positioning the mask with respect to the item PL. ;

A second object table (substrate) provided with a substrate holder 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 the item PL. Table) (WT); And

A projection system (" lens ") PL (e.g. refraction, car top) for imaging the irradiated portion of the mask MA onto the target portion C (including one or more dies) of the substrate W; Tricks or catadioptric optical systems).

As described herein, the apparatus is of a transmissive type (i.e. with a transmissive mask). In general, however, the device may for example be of a reflective type (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 (eg a mercury lamp or excimer laser) produces a radiation beam. The beam is supplied directly to the lighting system (illuminator) IL or via a conditioning means such as, for example, a beam expander Ex. The illuminator IL may comprise adjusting means AM for setting the outer and / or inner radial extent (commonly referred to as -outer and -inner, respectively) of the intensity distribution in the beam. It will also generally include a variety of other components such as integrator IN and capacitor CO. In this way, the beam PB incident on the mask MA has the desired uniformity and intensity distribution in its cross section.

In relation to FIG. 8, the source LA is placed in a housing of a lithographic packaging device (often as if the source LA is a mercury lamp, for example), but it is far from the lithographic projection device, It should be noted that the radiation beam it produces may enter the device (for example with the aid of a suitable directional mirror); This latter scenario is often the case when the source LA is an excimer laser (eg based on KrF, ArF or F ₂ lasing). The present invention encompasses both of these scenarios.

Thereafter, the beam PB intercepts the mask MA, which is held on the mask table MT. When the mask MA is crossed, the beam PB passes through the lens PL and focuses the beam PB on the target portion C of the substrate W. With the aid of the second positioning means (and interferometer measuring means IF) the substrate table WT can be precisely moved to position different target portions C in the path of the beam PB, for example. . Similarly, the first positioning means accurately locates the mask MA with respect to the path of the beam PB, for example after mechanical retrieval of the mask MA from the mask library or during scanning. Can be used to locate. In general, the movement of the object tables MT, WT is realized with the help of long-stroke modules (coarse positioning) and short-stroke modules (fine positioning). This will not be clearly shown in FIG. 8. However, in the case of a wafer stepper (as opposed to a step-and-scan tool) the mask table MT can only be connected or fixed to a single-stroke actuator.

The described tool can be used in two different modes:

In step mode the mask table MT is basically kept stationary, and the entire mask image is projected onto the target portion C at one time (ie in a single "flash"). Thereafter, the substrate table WT is shifted in the x and / or y directions so that different target portions C can be irradiated by the beam PB;

In scan mode, basically 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 (so-called "scan direction", for example y direction) at a velocity of v , and the projection beam PB is directed to scan the entire mask image. ; Simultaneously, the substrate table WT simultaneously moves in the same direction or the opposite direction at a speed V = Mv , where M is the magnification of the lens PL (typically M = 1/4 or 1/5). . In this way, a relatively wide target portion C can be exposed without degrading the resolution.

In addition, the software may implement or assist in the implementation of the disclosed concepts. Software functionality of a computer system involves programming comprising executable code and may be used to implement the imaging models described above. The software code may be executed by a general-purpose computor. In operation, the code and possibly associated data records are stored in a general purpose computer platform. At other times, however, the software may be moved and / or stored at other locations for loading into a suitable general purpose computer system. Thus, the above-described embodiments may involve one or more pieces of software in the form of one or more modules of code carried by one or more machine-readable media. Execution of such code by the processor of the computer system enables the platform to implement catalog and / or software downloading functions, essentially in the manner performed in the embodiments described and illustrated herein.

As used herein, the term computer or machine “readable medium” refers to any medium that participates in providing instructions to a processor for execution. Such media may take various forms, including but not limited to non-volatile media, volatile media, and transmission media. Non-volatile media includes, for example, optical or magnetic disks such as any storage device in any computer (s) operating as one of the server platforms described above. Volatile media includes dynamic memory, such as main memory of such computer platforms. Physical transmission media include coaxial cables, copper wire, and fiber optics, including wires that include a bus in a computer system. Carrier transmission media may take the form of electrical or electromagnetic signals, or acoustic or light waves, such as occur during radio frequency (RF) and infrared (IR) data communications. Therefore, common forms of computer-readable media include, for example: floppy disks, flexible disks, hard disks, magnetic tapes, any magnetic media, CD-ROMs, DVDs, any optical media, punch cards and Such as less commonly used media, paper tape, any physical media with a pattern of holes, RAM, PROM and EPROM, FLASH-EPROM, any memory chip or cartridge, carriers that carry data or instructions, such carriers The cables or links to deliver, or any other medium on 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.

Although the present invention has been described and illustrated in detail, it should be clearly understood that it is not intended to be present and to be limited only in the manner of illustration and illustration, and the scope of the present invention is limited only by the terms of the appended claims.

In accordance with the present invention, there is provided an improved CPL mask and method and computer program for generating the mask that can achieve satisfactory printing performance while minimizing the use of zebra patterns.

Claims (16)

In the method for generating a mask for printing a pattern comprising a plurality of features, Obtaining data indicative of the plurality of features; And Forming at least one of the plurality of features by etching the substrate to form a mesa, and depositing a chromium layer over the entire top surface of the mesa, Said mesa having a predetermined height. The method of claim 1, And the chromium layer has 0 percent light transmission. The method of claim 1, The chromium layer allows a predetermined percentage of light transmission. The method of claim 1, Said predetermined height of said mesa corresponds to a π phase shift or a 2π phase shift for light traversing said mesa. In computer programs, The computer comprising a computer-readable recording medium, the computer comprising means recorded on the recording medium for instructing the computer to generate a file representing a mask imaging a target pattern having a plurality of features. To control, This process, Obtaining data indicative of the plurality of features; And Defining at least one of the plurality of features to be formed by etching the substrate to form a mesa, and depositing a chromium layer over the entire top surface of the mesa, And the mesa has a predetermined height. The method of claim 5, And the chromium layer has a zero percent light transmittance. The method of claim 5, And the chromium layer allows a predetermined percentage of light transmission. The method of claim 5, And said predetermined height of said mesa corresponds to [pi] phase shift or 2 [pi] phase shift for light traversing the mesa. In the method for generating a mask for printing a pattern comprising a plurality of features, Obtaining data indicative of 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 shift material over the entire top surface of the mesa, Said mesa having a predetermined height. The method of claim 9, And wherein the light transmissive phase shift material has a predetermined percentage of transmittance and a predetermined phase shift. The method of claim 9, And said predetermined height of said mesa corresponds to [pi] phase shift or 2 [pi] phase shift for light traversing the mesa. In computer programs, The computer comprising a computer-readable recording medium, the computer comprising means recorded on the recording medium for instructing the computer to generate a file representing a mask imaging a target pattern having a plurality of features. To control, This process, Obtaining data indicative of the plurality of features; And Defining at least one of the plurality of features to be formed by etching the substrate to form a mesa, and depositing a light transmissive phase shift material over the entire top surface of the mesa, And the mesa has a predetermined height. The method of claim 12, And the light transmissive phase shift material has a predetermined percentage of transmittance and a predetermined phase shift. The method of claim 12, And said predetermined height of said mesa corresponds to [pi] phase shift or 2 [pi] phase shift for light traversing the mesa. In the device manufacturing method, (a) providing a substrate wholly or partially covered by a layer of radiation sensitive material; (b) providing a projection beam of radiation using an imaging system; (c) generating a mask used to impart a pattern to the cross section of the projection beam; (d) projecting a patterned beam of radiation onto a target portion of the layer of radiation sensitive material, In step (c), the mask is, Obtaining data indicative of the plurality of features; And Forming at least one of the plurality of features by etching the substrate to form a mesa, and depositing a chromium layer over the entire top surface of the mesa, Said mesa having a predetermined height. In the device manufacturing method, (a) providing a substrate wholly or partially covered by a layer of radiation sensitive material; (b) providing a projection beam of radiation using an imaging system; (c) generating a mask used to impart a pattern to the cross section of the projection beam; (d) projecting a patterned beam of radiation onto a target portion of the layer of radiation sensitive material, In step (c), the mask is, Obtaining data indicative of the plurality of features; And Defining at least one of the plurality of features to be formed by etching the substrate to form a mesa, and depositing a light transmissive phase shift material over the entire top surface of the mesa, Said mesa having a predetermined height.

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