OPPORTUNISTIC PLACEMENT OF IC TEST STRUCUTRES AND/OR E-BEAM TARGET PADS IN AREAS OTHERWISE USED FOR FILLER CELLS, TAP CELLS, DECAP CELLS, SCRIBE LINES, AND/OR DUMMY FILL, AS WELL AS PRODUCT IC CHIPS CONTAINING SAME
Product ICs/wafers include additional diagnostic, test, or monitoring structures opportunistically placed in filler cell positions, within tap cells, within decap cells, within scribe line areas, and/or within dummy fill regions. Improved fabrication processes utilize data from such structure(s) in wafer disposition decisions, rework decisions, process control, yield learning, or fault diagnosis.
This application is a continuation of U.S. patent application Ser. No. 14/303,578, filed Jun. 12, 2014, which '578 application is a continuation-in-part of U.S. patent application Ser. No. 14/190,040, filed Feb. 25, 2014, which is a continuation-in-part of U.S. patent application Ser. No. 14/038,799, filed Sep. 27, 2013. This application also claims priority from the following Provisional U.S. Patent Applications: Ser. No. 61/942,163, filed Feb. 20, 2014; Ser. No. 61/971,306, filed Mar. 27, 2014; Ser. No. 61/972,787, filed Mar. 31, 2014; Ser. No. 61/982,652, filed Apr. 22, 2014; and Ser. No. 62/011,161, filed Mar. 12, 2014. Each of the '578, '040, '799, '163, '306, '787, '652 and '161 applications is incorporated by reference herein.
FIELD OF THE INVENTIONThis invention relates to the field of semiconductor integrated circuits and to methods for manufacturing and testing such circuits.
BACKGROUND OF THE INVENTIONPlacement of “test structures” (defined herein as any patterning not required for circuit functioning, but designed, intended or used for monitoring or evaluation of the fabrication process or resultant partially or fully fabricated wafers/chips) on product wafers, has become commonplace over the last decade. Traditionally, such test structures are located in the scribe line areas between active die. See, e.g., Hess, Christopher, et al., “Scribe characterization vehicle test chip for ultra fast product wafer yield monitoring,” IEEE International Conference on Microelectronic Test Structures, 2006.
U.S. Pat. No. 7,223,616 B2 (“Test Structures in Unused Areas of Semiconductor Integrated Circuits and Methods for Designing the Same”) to F. Duan, et al. describes the placement of interconnected, active test cells beneath the probe pads of test and product wafers.
U.S. Pat. No. 7,679,083 B2 (“Semiconductor integrated test structures for electron beam inspection of semiconductor wafers”) to S. Jansen, et al. describes the placement of test structures within large, pre-designated regions of product ICs.
While these and other known techniques that locate test structures on product wafers produce useful results, they are still less than ideal. Specifically, the area available in the scribe line of product wafers is strictly limited and can only accommodate certain types of test structures. Additionally, both the in-the-scribe-line and under-the-probe-pad methods suffer from the fact that the test structures are located far away from the most important active circuitry regions, and are thus not likely to accurately represent the processing environment of the active circuitry. Although the '083 patent can potentially mitigate this problem, it does so at the unacceptable cost of requiring large, dedicated test regions (see '083 patent, FIG. 5, regions 44-45) that consume otherwise precious active die area.
SUMMARY OF THE INVENTIONThe present invention discloses several techniques for improving test structure coverage on product ICs with little or no sacrifice of active die area.
In accordance with one aspect of the invention, “filler cells” (defined as non-functional cells placed within the active circuitry region for the purpose of avoiding/relieving routing congestion and/or equalizing cell density) are replaced with self-contained test structures that do not require additional area or interconnect. Modern, standard-cell layouts commonly use such filler cells to relieve routing congestion. See, e.g., Cong, J., et al. “Optimizing routability in large-scale mixed-size placement,” ASP-DAC, 2013; and Menezes, C., et al. “Design of regular layouts to improve predictability,” Proceedings of the 6th IEEE International Caribbean Conference on Devices, Circuits and Systems, 2006. While PCT Applic. WO 2009/090516 A1 (“Monitor Cell and Monitor Cell Placement Method”) to C. Mayor, et al. proposes the idea of replacing a filler cell with a “monitor cell” (see FIG. 5, step 540), the proposed monitor cell is much too large to fit into a filler cell space and, even more importantly, requires additional interconnect for integration into a scan chain. Examples of test-enabled filler (Fill) cells suitable for use in connection with the invention are disclosed in the '163 provisional application, and in
In accordance with another aspect of the invention, decap (decoupling capacitance) cells are modified to incorporate one or more self-contained test structures. Use of such decap cells is well known in the art. See, e.g., X. Meng, et al., “Novel Decoupling Capacitor Designs for sub-90 nm CMOS Technology,” Proceedings of the 7th IEEE International Symposium on Quality Electronic Design, 2006.
In accordance with another aspect of the invention, well tap (tap) cells are modified to incorporate one or more self-contained test structures. Use of such tap cells is well known in the art. See, e.g., U.S. Pat. No. 6,388,315 (“Tap connections for circuits with leakage suppression capability”), incorporated by reference herein; Jungeblut, T., et al., 2010, “A modular design flow for very large design space exploration,” at FIG. 4 (“- add well tap cells”). Examples of such test-enabled tap cells are disclosed in the '163 provisional application.
In accordance with still another aspect of the invention, “dummy fill” areas (see U.S. Pat. No. 7,137,092 B2, incorporated by reference herein) are populated with test structure patterns.
U.S. Pat. No. 7,217,579 (“Voltage contrast test structure”) and U.S. Pat. No. 7,679,083 (“Semiconductor integrated test structures for electron beam inspection of semiconductor wafers”), both incorporated by reference herein, disclose the use of voltage contrast test structures in the scribe line areas of semiconductor wafers. Another aspect of the present invention involves the use of scribe line areas for additional test structure insertion. Such scribe line areas can be advantageously used to implement test structures whose use might be discouraged or prohibited within the active die areas of product wafers, either because of actual performance issues or requirements for compatibility with existing DRC (design rule checking) flows. Examples of such discouraged/prohibited test structures include structures that involve intentional inter-layer misalignment(s), sub-design rule or canary structures, or structures whose density or patterning is incompatible with requirements in the active die area. See, for example, abandoned U.S. Patent Applic. No. 2009-0102501 A1 (“Test structures for e-beam testing of systematic and random defects in integrated circuits”), incorporated herein by reference, for examples of e-beam compatible canary test structures. In certain embodiments of this invention, inter-die scribe line areas of the inventive product IC wafers are entirely or mostly populated with voltage contrast test structures whose use within the active die areas would be discouraged or prohibited.
Another aspect of the invention involves the opportunistic insertion of test pads (a type of “test structure,” as hereinabove defined) into the dummy fill, filler cell, decap cell, and/or tap cell positions noted above (and/or within such cells). Such test pads preferably comprise charged particle (e.g., e-beam) targets, preferably sized in the smaller dimension to be in the range of 1× to 10× of the minimum resolvable feature size at a given technology node, but may also comprise micro- or nano-probeable contact pads. Such test pads may be positioned above associated test structures, adjacent to associated test structures, connected to non-adjacent test structures on the same layer, or connected to associated test structures on lower layer(s).
Other aspects of the invention relate to ICs and IC layouts having one, two, three, or four of the above-noted types of opportunistically inserted test structures, either with or without the traditional scribe-line and under-the-pad test structures. Still further aspects of the invention relate to CAD methods for forming such IC layouts, to fabrication process that utilize, at least in part, information obtained from the inventive, opportunistically inserted test structures, and to ICs manufactured thereby.
Accordingly, generally speaking, and without intending to be limiting, certain aspects of the invention relate to product ICs that contain, for example: at least ten, twenty, thirty, or more rows of at least fifty, seventy-five, one-hundred or more abutting cells; characterized in that: each of the rows includes a plurality of logic cells; and at least half, three-quarters or more of the rows include a test structure in a filler, decap, or tap cell position (and/or within such cells). Such product ICs may additionally contain a plurality of dummy fill test structures (including, but not limited to, test pads) implemented in dummy fill regions that at least partially overlay the rows. Such dummy fill test structures may appear on any patterned layer and, in particular, on one, or more than one metal layer.
Each of the test structures is preferably self-contained, thereby not requiring use of routing areas for on-chip connections. In other words, in accordance with this self-contained aspect of the invention, replacing the filler/decap/tap cells with the inventive test cells/structures should not affect the available routing areas. In some embodiments, such self-contained test structures may be formed in the footprints of multiple, adjacent filler, decap, or tap cells, thus allowing even larger and/or irregularly shaped self-contained test structures. Such product ICs may contain test structures that are configured for e-beam testing, test structures that are configured for SEM inspection, test structures that are configured for bright field inspection, test structures that are configured for probe contacting (by microprobe, nanoprobe or probe card), or any combination of two, three, or four of these.
Again, generally speaking, and without intending to be limiting, other aspects of the invention relate to product ICs that contain, for example: a contiguous region containing at least twenty, thirty, forty, or more adjacent rows of at least one-hundred, one-hundred-fifty, two-hundred or more abutting cells, with routing areas; characterized in that: each of the rows includes a majority (or a super-majority, such as 60%, 70%, or 80%) of logic cells; and the contiguous region also contains at least twenty-five (or 50, 100, 150, or more) irregularly distributed, self-contained test structures, each positioned in one of the rows, in a position otherwise suitable for a logic cell, or a filler cell, or a tap cell. In some embodiments, at least some of the test structures are contained within decap cells. Such product ICs may also include a plurality of self-contained, dummy fill test structures, each at least partially overlying the contiguous region, but not connected to any of the logic cells (excluding connections to common power nets). In some embodiments, such dummy fill test structures may occupy more than one interconnect layer. In some embodiments, at least some of said test structures are canary (i.e., sub-Design Rule) test structures, and at least some of the dummy fill test structures are random defect test structures. In other embodiments, test structures may comprise DR-compliant structures configured to test for, or evaluate, systematic failure modes. And embodiments that comprise combinations of these are contemplated as well.
Again, generally speaking, and without intending to be limiting, other aspects of the invention relate to IC fabrication processes that include, for example, at least the steps of: subjecting an IC wafer to initial fabrication steps; obtaining measurements from at least five (or 10, 20, 40 or more) self-contained test structures, opportunistically distributed within a contiguous logic portion of the wafer; and, based at least in part, on measurements obtained from the test structures, selectively subjecting the wafer to additional and/or modified fabrication steps. In certain embodiments, obtaining measurements may involve exciting the test structures by charged particles (such as by e-beam), inspecting the test structures by bright field inspection, inspecting the test structures by SEM inspection, or contacting the test structures by probing for electrical measurement. In certain embodiments, selectively subjecting the wafer to additional fabrication steps or Physical Failure Analysis may involve determining whether to rework one or more of the initial fabrication steps, or determining whether or not to perform the additional fabrication steps, or discard the wafer.
Again, generally speaking, and without intending to be limiting, a process for making a product IC wafer, in accordance with certain embodiments of the invention, may illustratively comprise at least the following steps: obtaining an initial product wafer layout; using a computer to analyze the initial product wafer layout and identify areas of opportunity (e.g., dummy fill, filler cells, tap cells, decap cells) for test structure insertion; using the computer to modify the initial product wafer layout by inserting a plurality of test structures that collectively make up at least one distributed DOE across the areas of opportunity identified for test structure insertion; storing information necessary to fabricate the modified product wafer layout, but not information needed to utilize the distributed DOE(s), in a computer-readable layout data record; storing information needed to utilize the distributed DOE(s) in a computer-readable test data record; and, providing information from the layout data record to a fabricator in order to enable fabrication of a wafer based on the modified product wafer layout. In accordance with this, and other, aspects of the invention, such layout modifications can proceed either during the design flow (i.e., before design sign-off) or during a subsequent mask data processing (MDP) step(s), or during both. In accordance with a related aspect of the invention, a method for making IC product chips may illustratively comprise at least the following steps: receiving a first product IC wafer comprising multiple product IC dies with embedded test structures that collectively make up at least one distributed DOE; receiving data that identifies and enables use of at least one of the distributed DOE(s); utilizing the at least one distributed DOE(s) to obtain information concerning the fabrication of the first product IC wafer; and, processing the first product IC wafer into multiple IC product chips. Such methods may further comprise at least the following additional steps: receiving a second product IC wafer identical to the first product IC wafer; utilizing at least one of the distributed DOE(s) on the second product IC wafer to obtain information concerning the fabrication of the second product IC wafer; and, processing the second product IC wafer into multiple IC product chips. In accordance with these aspects of the invention, data from such DOE(s) and/or test structure(s) may be utilized in wafer disposition decisions, rework decisions, process control, yield learning, or fault diagnosis.
Again, generally speaking, and without intending to be limiting, a product IC wafer, in accordance with another aspect of the invention, may comprise at least: an area of functional product circuitry, with a multiplicity of e-beam exercisable test structures (or pads/targets) distributed within the area of functional product circuitry; and, a plurality of e-beam skip zones, each of which allows an e-beam scanner to skip at least 10%, 15%, or 20% of its overall scan length (measured in the scan direction) without missing the opportunity to exercise any test structures (or pads/targets). Such product IC wafers may preferably further include at least: one or more empty e-beam scanning tracks, each spanning the entire width of the area of functional product circuitry.
Again, generally speaking, and without intending to be limiting, another aspect of the invention relates to product wafers that contain, for example, at least the following: an array of at least three-by-three (or five-by-five, ten-by-ten, twenty-by-twenty, or fifty-by-fifty, etc.) product die, with scribe line areas separating the product die; with the wafers characterized in that: each of the product dies includes a (large) plurality of operable (combinational and/or sequential) logic cells that support product functionality; each of the product dies includes a plurality of test-enabled tap cells, interspersed with the logic cells, wherein each of the test-enabled tap cells comprises a self-contained voltage contrast test structure (with or without an e-beam test pad); and, each of the scribe line areas contains a plurality of voltage contrast test structures (with or without corresponding e-beam test pads). Such product dies may further include: a plurality of test-enabled decap cells, wherein each of the test-enabled decap cells comprises a self-contained voltage contrast test structure (with or without corresponding e-beam test pads); a plurality of test-enabled filler cells, wherein each of the test-enabled filler cells comprises a self-contained voltage contrast test structure (with or without corresponding e-beam test pads); and/or a plurality of self-contained voltage contrast test structures implemented in dummy fill regions of said product dies (with or without corresponding e-beam test pads). In certain embodiments, the scribe line areas are substantially fully populated with voltage contrast test structures (including e-beam target pads), and some or a majority of the test structures contained in the scribe line areas may comprise canary structures, contain intentional layer misalignments, and/or contain intentional violations of process design rules.
Again, generally speaking, and without intending to be limiting, another aspect of the invention relates to IC fabrication processes that comprise, for example, at least the following steps: subjecting a product IC wafer to initial fabrication steps; obtaining e-beam excited measurements from at least forty (preferably, at least one hundred) self-contained test structures, at least twenty of the test structures irregularly distributed within a contiguous logic portion of the wafer (i.e., portion of the wafer that contains functional product logic), and at least twenty of the test structures located within scribe line portions of the wafer; and, based, at least in part, on measurements obtained from the test structures, selectively subjecting the wafer to additional fabrication steps. In certain preferred embodiments, obtaining measurements comprises selectively targeting e-beam target pads located in the scribe line areas of the wafer, without continuously scanning any substantial portion of the wafer (by, for example, sampling a single pixel value, or fewer than ten pixel values). In certain preferred embodiments, obtaining measurements comprises selectively targeting e-beam target pads located within the contiguous logic portion of the wafer, without continuously scanning any substantial portion of the wafer. In some embodiments, selectively subjecting may include determining whether to rework one or more of the initial fabrication steps. And in some embodiments, selectively subjecting may include determining whether or not to perform the additional fabrication steps.
Certain embodiments of the invention may include electrically probeable test structures, including but not limited to the type described in the '652 provisional application, located in the scribe line regions of product wafers. Such electrically probeable test structures may include their own probe pads, or may share one or more pads with nearby voltage-contrast test structures, thereby allowing single pads to function both as a probe pads and e-beam target pads.
In the discussion that follows, the inventive cells (of
Generally speaking, and without intending to be limiting, additional aspects of the invention relate to product integrated circuits that contain, within a contiguous logic region of at least 500 (or 1000, 1500, etc.) cells, (i) at least a select number (e.g., three, four, five, six, seven, etc.) of distinct functional cells selected from the set consisting of: a
Again, Generally speaking, and without intending to be limiting, additional aspects of the invention relate to product integrated circuits that contain, within a contiguous logic region of at least 200 (or 500, 1000, etc.) means, (i) at least a select number (2, 3, 4, 5, etc.) of distinct “means” (i.e., the corresponding means or the §112 ¶6 “equivalent thereof”) selected from the set consisting of: a
While the exemplary logic and test-enabled cells (
Another aspect of this invention relates to the use of a tool using a charged particle column (electrons or ions), whose primary function is to find defects on the surface of semiconductor wafers (i.e., function as an inspector). (While the present description uses the term “e-beam,” it is understood that it applies to all charged beams.)
In accordance with one aspect of the invention, we describe a VC inspector that samples pixels on a wafer surface. This method of scanning is fundamentally different from all inspectors designed before. In one embodiment, the pixels have certain designated X-Y coordinates whose pixel value (i.e., electron beam signal) is used to determine if a defect exists or not. This can be viewed as a 0-D inspection, instead of the typical 2-D inspection of the prior art.
In one embodiment, the pixel corresponds to a “pad” in an electrical test structure that is specifically created for the purpose finding a voltage contrast defect. The beam shines on the pad for a designated length of time. Each test structure may have one or more pads (inspector reads out one pixel per pad). Such test pads may exist on a semiconductor wafer whose patterns have been designed primarily as a “test chip,” or may be embedded in a “product wafer.”
In one embodiment, each pixel corresponds to a certain specific location of a semiconductor product layout. These pixels are selected because a signal abnormality at these locations on the product are indicative of a specific type or types of defect.
In one embodiment, the stage is held stationary akin to “step and scan” inspection. Once the pixel values corresponding to a given field of view are sensed, the stage moves to another location where the next set of pixels can be read out.
In one embodiment, the stage is moving when the pixels are being scanned and the inspection happens by deflecting the e-beam accordingly to account for the motion of the stage.
In one embodiment, the duration of the pixel readout at each location is dynamic with respect to each pixel, i.e., depending on the test structure or product circuit being inspected at each point, the duration of the beam hold at the location is changed suitably.
In one embodiment, the size of the beam on the wafer is not fixed, but is changed dynamically for each location being read out. This type of beam shaping is similar to what is used in e-beam writers. The sizing of the spot on a per structure basis allows the beam to be optimized with respect to each structure. The optimization is typically to maximize the signal-to-noise ratio of the inspection. Another aspect of the invention relates to design of a voltage-contrast device-under-test (“VC DUT”), with a test pad, where the complete structure is tested with very few pixels (<10). Such a VC DUT may have a test pad whose size and shape accommodates non-circular incident e-beams, while maximizing SNR at the same time. Such beams may also be square shaped to match pads that are similarly square shaped. Such pads may be configured to capture beams with an asymmetric aspect ratio (X/Y length ratio) that is greater than 3 (e.g., DUT with an X-dimension of 100 nm and Y dimension 300-600 nm would have aspect ratio of 3:1, 4:1, 5:1).
These, as well as other, aspects, features and advantages of the present invention are exemplified in the following set of drawings, in which:
As persons skilled in the art will recognize, numerous options exist for the selection of particular test structures to be opportunistically instantiated in accordance with the present invention.
Product ICs in accordance with the invention may include test structures adapted for in-line systematic defect inspection, by bright field and/or e-beam (or other charging), of product layout patterns most susceptible to systematic defects, including multi-patterning structures. Such test structures preferably include canary structures (i.e., sub-design rule structures used to explore process-layout marginalities).
Product ICs in accordance with the invention may also include test structures adapted for in-line random defect inspection, by bright field and e-beam tools, of product-like patterns for the most likely defects, such as single line opens and most likely via open locations (including canary structures).
Product ICs in accordance with the invention may also include test structures adapted for in-line metrology, such as structures to extract overlay/misalignment, product-specific patterns for poly CD, MOL CD, via bottom CD, metal CD and height, dielectric heights, etc., and may be testable electrically and/or by Scanning Electron Microscope (e.g., for overlay, line CD and profile).
Product ICs in accordance with the invention may also include Physical Failure Analysis (PFA) structures for likely systematic defects, where such PFAs may include product specific layout patterns (including canary structures) and pads for probing.
And product ICs in accordance with the invention may also include any combination of the above-noted, or other, usable test structures.
For test-enabled decap cells, the preferred test structures are M1 structures for Single Line Open inspection.
Important goals for the design of test structures in accordance with certain embodiments of the invention are that: (1) test structures should not affect printability of the active geometry (i.e., standard cells or interconnect), and/or (2) test structures should be representative of the active cell properties (printability and electrical characteristics).
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As persons skilled in the art will appreciate, the exemplary flip-flop, latch, and mux designs depicted in
For a functioning DUT, the pad lines will appear as alternating bright/dark, whereas for a non-functioning DUT (i.e. one that has failed), pads are all bright or all dark. The advantage here is that the “net” gray level for all non-defective DUTs is effectively always the same, and the image computer can use the same thresholds for the detection of all defective DUTs. This simplifies the software algorithm and the hardware of the image computer.
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The beam and pad are designed to have more or less the same footprint. In this case, the X/Y aspect ratio ˜1. Beam is square shaped to match the pad, but could also be circular with similar size. Pictograph shows four pads, but the invention applies to one or multiple pads equivalently.
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Claims
1. An IC fabrication process, comprising at least the following steps:
- subjecting a product IC wafer to initial fabrication steps;
- obtaining e-beam excited measurements, without continuously scanning, from a plurality of test structures by selectively sampling fewer than ten pixels from an e-beam pad associated with each of said test structures; and, based, at least in part, on measurements obtained from said test structures, selectively subjecting the wafer to additional fabrication steps.
2. An IC fabrication process, as defined in claim 1, wherein obtaining measurements comprises selectively targeting e-beam target pads having an asymmetric aspect ratio.
3. An IC fabrication process, as defined in claim 1, wherein obtaining measurements involves obtaining only a single pixel measurement from each targeted e-beam pad.
4. An IC fabrication process, as defined in claim 1, wherein selectively subjecting comprises determining whether to rework one or more of the initial fabrication steps.
5. An IC fabrication process, as defined in claim 1, wherein selectively subjecting comprises determining whether or not to perform the additional fabrication steps.
6. An IC fabrication process, comprising at least the following steps:
- subjecting a product IC wafer to initial fabrication steps;
- obtaining e-beam excited measurements from a plurality of test structures by selectively targeting, using an e-beam spot with an elongated major axis, an e-beam pad associated with each of said test structures; and,
- based, at least in part, on measurements obtained from said test structures, selectively subjecting the wafer to additional fabrication steps.
7. An IC fabrication process, as defined in claim 6, wherein each of the targeted e-beam pads has at least one of its dimensions matched to the elongated major axis of the e-beam spot, so as to maximize scanning efficiency.
8. An IC fabrication process, as defined in claim 6, wherein each of the targeted e-beam pads has a first one of its dimensions matched to the elongated major axis of the e-beam spot, and wherein at least some of the targeted e-beam pads vary in a second dimension perpendicular to said first dimension.
9. An IC fabrication process, as defined in claim 6, wherein each of the targeted e-beam pads is positioned along a linear scan line, and wherein the elongated major axis of the e-beam spot is oriented perpendicular to the scan line.
10. An IC fabrication process, as defined in claim 6, wherein obtaining measurements involves obtaining fewer than ten pixel measurements from each targeted e-beam pad.
11. An IC fabrication process, as defined in claim 10, wherein obtaining measurements involves obtaining only a single pixel measurement from each targeted e-beam pad.
12. An IC fabrication process, as defined in claim 6, wherein selectively subjecting comprises determining whether to rework one or more of the initial fabrication steps.
13. An IC fabrication process, as defined in claim 6, wherein selectively subjecting comprises determining whether or not to perform the additional fabrication steps.
14. An IC fabrication process, comprising at least the following steps:
- subjecting a product IC wafer to initial fabrication steps;
- obtaining e-beam excited measurements from a plurality of test structures by selectively targeting, along a linear scan direction, an e-beam pad associated with each of said test structures, wherein each targeted e-beam pad comprises a plurality of electrically connected, elongated metal segments; and,
- based, at least in part, on measurements obtained from said test structures, selectively subjecting the wafer to additional fabrication steps.
15. An IC fabrication process, as defined in claim 14, wherein each of the targeted e-beam pads has at least two elongated metal segments that are identical in size and shape.
16. An IC fabrication process, as defined in claim 14, wherein obtaining measurements involves obtaining fewer than ten pixel measurements from each targeted e-beam pad.
17. An IC fabrication process, as defined in claim 16, wherein obtaining measurements involves obtaining only a single pixel measurement from each targeted e-beam pad.
18. An IC fabrication process, as defined in claim 14, wherein obtaining measurements involves selectively targeting, using an e-beam spot with an elongated major axis oriented perpendicular to the linear scan direction.
19. An IC fabrication process, as defined in claim 14, wherein selectively subjecting comprises determining whether to rework one or more of the initial fabrication steps.
20. An IC fabrication process, as defined in claim 14, wherein selectively subjecting comprises determining whether or not to perform the additional fabrication steps.
Type: Application
Filed: Feb 3, 2015
Publication Date: Sep 24, 2015
Inventors: Indranil De (San Jose, CA), Dennis J. Ciplickas (San Jose, CA), Stephen Lam (Freemont, CA), Jonathan Haigh (Pittsburgh, PA), Vyacheslav V. Rovner (Pittsburgh, PA), Christopher Hess (Belmont, CA), Tomasz W. Brozek (Morgan Hill, CA), Andrzej J. Strojwas (Pittsburgh, PA), Kelvin Doong (Zhubei City), John K. Kibarian (Los Altos, CA), Sherry F. Lee (Monte Sereno, CA), Kimon W. Michaels (Monte Sereno, CA), Marcin A. Strojwas (Pittsburgh, PA), Conor O'Sullivan (Campbell, CA), Mehul Jain (San Jose, CA)
Application Number: 14/612,841