Patent Publication Number: US-8969166-B2

Title: Method and apparatus for selectively improving integrated device performance

Description:
RELATED APPLICATIONS 
     The present Application for Patent claims priority from and is a divisional application of U.S. patent application Ser. No. 13/328,912, entitled “METHOD AND APPARATUS FOR SELECTIVELY IMPROVING INTEGRATED DEVICE PERFORMANCE”, filed Dec. 16, 2011 and assigned to the assignee hereof and hereby expressly incorporated by reference herein, which claims priority to U.S. Provisional Application No. 61/472,449, entitled “METHOD AND APPARATUS FOR SELECTIVELY IMPROVING INTEGRATED DEVICE PERFORMANCE,” filed Apr. 6, 2011 and assigned to the assignee hereof and hereby expressly incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     This disclosure relates generally to electronics, and more specifically, but not exclusively, to apparatus and methods for selectively improving integrated device performance. 
     BACKGROUND 
     In mobile systems-on-a-chip (SOC), chip performance is becoming increasingly important to benchmark against competition. The traditional approach is to design an integrated circuit (IC) using transistor models and simulate it at certain voltage, temperature, and process corners to ensure the IC meets certain performance criteria. Once design is complete, the IC is manufactured according to the transistor specifications used by the design. Thus, performance of the IC is fixed at the design operating conditions. However, customers continuously demand improvements in IC performance. It is highly desirable to have an IC that outperforms a competitor&#39;s product to differentiate over competitor devices. Conventional methods dictate that product improvement requires redesigning the entire IC. However, redesigning the entire IC requires very high reengineering costs and long cycle times. What is needed are IC design and fabrication techniques that increase IC performance without sacrificing standby (i.e., sleep-mode) leakage, and without requiring repetitive redesign of the entire IC. 
     Accordingly, there are long-felt industry needs for methods and apparatus that mitigate problems of conventional methods and apparatus, including selectively improving IC performance. 
     SUMMARY 
     This summary provides a basic understanding of some aspects of the present teachings. This summary is not exhaustive in detail, and is neither intended to identify all critical features, nor intended to limit the scope of the claims. 
     Exemplary methods and apparatus for selectively improving integrated circuit performance are provided. In an example, a method includes defining a critical portion of an integrated circuit layout that determines the speed of the integrated circuit; identifying at least a part of the critical portion that includes at least one of a halo implant region, lightly doped drain (LDD) implant region, and source drain extension (SDE) implant region; and performing a speed push flow process to increase performance of the part of the critical portion that includes the at least one of the halo implant region, the LDD implant region, and the SDE implant region. The method can also include masking a first portion of the integrated circuit that includes the halo implant region and is outside the critical portion; implanting a first halo implant in the portion of the integrated circuit that includes the halo implant region and is inside the critical portion; masking a second portion of the integrated circuit that includes the halo implant region and is inside the critical portion; and implanting a second halo implant in the portion of the integrated circuit, that includes the halo implant region and is outside the critical portion, where the second halo implant receives a higher dose of dopant than the first halo implant. 
     Furthermore, the method can also include fabricating a first portion the integrated circuit that includes the halo implant region and is outside the critical portion with first polycrystalline silicon gates having a width based on a first critical dimension; and fabricating a second portion of the integrated circuit that includes the halo implant region and is inside the critical portion with second polycrystalline gates having a width based on a second critical dimension, where the first critical dimension is greater than the second critical dimension. Further, the method can also include fabricating a first portion of the integrated circuit that includes the halo implant region and is outside the critical portion with a first gate oxide layer having a first thickness; and fabricating a second portion of the integrated circuit that includes the halo implant region and is inside the critical portion second with a gate oxide layer having a second thickness, where the first thickness is greater than the second thickness. 
     Moreover, the method can include fabricating a first portion of the integrated circuit that includes the LDD implant region and is outside the critical portion with a first dopant concentration; and fabricating a second portion of the integrated circuit that includes the LDD implant region and is inside the critical portion with a second dopant concentration, where the first dopant concentration is less than the second dopant concentration. In another example, the method can also include fabricating a first portion of the integrated circuit that includes the SDE implant region and is outside the critical portion with a first dopant concentration; and fabricating a second portion of the integrated circuit that includes the SDE implant region and is inside the critical portion with a second dopant concentration, where the first dopant concentration is less than the second dopant concentration. 
     In a further example, provided is a non-transitory computer-readable medium, comprising instructions stored thereon that, if executed by a lithographic device, cause the lithographic device to execute at least a part of the aforementioned method. 
     In another example, provided is an apparatus configured to selectively improve integrated circuit performance. The apparatus includes means for defining a critical portion of an integrated circuit layout that determines the speed of the integrated circuit; means for identifying at least a part of the critical portion that includes at least one of a halo implant region, lightly doped drain (LDD) implant region, and source drain extension (SDE) implant region; and means for performing a speed push flow process to increase performance of the part of the critical portion that includes the at least one of the halo implant region, the LDD implant region, and the SDE implant region. The apparatus can also include means for masking a first portion of the integrated circuit that includes the halo implant region and is outside the critical portion; means for implanting a first halo implant in the portion of the integrated circuit that includes the halo implant region and is inside the critical portion; means for masking a second portion of the integrated circuit that includes the halo implant region and is inside the critical portion; and means for implanting a second halo implant in the portion of the integrated circuit that includes the halo implant region and is outside the critical portion, where the second halo implant receives a higher dose of dopant than the first halo implant. 
     The apparatus can also include means for fabricating a first portion of the integrated circuit that includes the halo implant region and is outside the critical portion with first polycrystalline silicon gates having a width based on a first critical dimension; and means for fabricating a second portion of the integrated circuit that includes the halo implant region and is inside the critical portion with second polycrystalline gates having a width based on a second critical dimension, where the first critical dimension is greater than the second critical dimension. Further, the apparatus can also include means for fabricating a first portion of the integrated circuit that includes the halo implant region and is outside the critical portion with a first gate oxide layer having a first thickness; and means for fabricating a second portion of the integrated circuit that includes the halo implant region and is inside the critical portion second with a gate oxide layer having a second thickness, where the first thickness is greater than the second thickness. 
     Furthermore, in an example, the apparatus includes means for fabricating a first portion of the integrated circuit that includes the LDD implant region and is outside the critical portion with a first dopant concentration; and means for fabricating a second portion of the integrated circuit that includes the LDD implant region and is inside the critical portion with a second dopant concentration, where the first dopant concentration is less than the second dopant concentration. Moreover, the apparatus can also include means for fabricating a first portion of the integrated circuit that includes the SDE implant region and is outside the critical portion with a first dopant concentration; and means for fabricating a second portion of the integrated circuit that includes the SDE implant region and is inside the critical portion with a second dopant concentration, where the first dopant concentration is less than the second dopant concentration, 
     In another example, provided is an integrated circuit fabricated according to an integrated circuit layout. The integrated circuit includes a critical portion of the integrated circuit layout that determines a speed of the integrated circuit, where at least a part of the critical portion includes at least one of a halo, lightly doped drain (LDD), and source drain extension (SDE) implant region; and a marker layer comprising the part of the critical portion that includes the at least one of the halo, the lightly doped drain (LDD), or the source drain extension (SDE) implant region, and that includes at least one transistor formed therefrom. In an example, a first transistor in the critical portion has a first halo implant, a second transistor outside of the critical portion has a second halo implant; and the first halo implant has a higher dopant concentration than the second halo implant. In another example, the first transistor in the critical portion includes a first polycrystalline silicon gate, and a second transistor outside of the critical portion has a second polycrystalline silicon gate, where the first polycrystalline silicon gate has a smaller critical dimension than the second polycrystalline silicon gate. 
     In a further example, a first transistor in the critical portion has a first gate oxide having a first thickness, a second transistor outside of the critical portion has a second gate oxide having a second thickness; and the first thickness is thinner than the second thickness. In another example, a first transistor in the critical portion has the LDD having a first dopant concentration, a second transistor outside of the critical portion has a second LDD having a second dopant concentration; and the first dopant concentration is greater than the second dopant concentration. In another example, a first transistor in the critical portion has an SDE implant having a first dopant concentration, a second transistor outside of the critical portion has a second SDE implant having a second dopant concentration; and the first dopant concentration is greater than the second dopant concentration. 
     At least a part of the integrated circuit can be integrated in a semiconductor die. Further, at least a part of the integrated circuit can be integrated with a mobile device. In a further example, provided is a non-transitory computer-readable medium, comprising instructions stored thereon that, if executed by a lithographic device, cause the lithographic device to fabricate at least a part of the integrated circuit. 
     The foregoing broadly outlines some of the features and technical advantages of the present teachings in order that the detailed description and drawings can be better understood. Additional features and advantages are also described in the detailed description, The conception and disclosed embodiments can be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present teachings. Such equivalent constructions do not depart from the technology of the teachings as set forth in the claims. The novel features that are characteristic of the teachings, together with further objects and advantages, are better understood from the detailed description and the accompanying figures. Each of the drawings is provided for the purpose of illustration and description only, and does not limit the present teachings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are presented to describe examples of the present teachings, and are not provided as limitations. 
         FIG. 1  depicts an exemplary n-channel transistor halo implant in integrated circuit. 
         FIG. 2  depicts a typical n-channel transistor halo implant process. 
         FIG. 3  depicts an exemplary n-channel transistor halo implant speed push flow process. 
         FIG. 4  depicts a typical polycrystalline gate fabrication process. 
         FIG. 5  depicts an exemplary polycrystalline gate critical dimension speed push flow process. 
         FIG. 6  depicts a typical gate oxide fabrication process. 
         FIGS. 7A-B  depict an exemplary gate oxide speed push flow process. 
         FIGS. 8A-8F  depict exemplary methods for selectively improving integrated circuit performance. 
     
    
    
     The features depicted by the drawings may not be drawn to scale. Accordingly, the dimensions of the depicted features may be arbitrarily expanded or reduced for clarity. In accordance with common practice, some of the drawings are simplified for clarity. Thus, the drawings may not depict all components of a particular apparatus or method. Further, like reference numerals denote like features throughout the specification and figures. 
     DETAILED DESCRIPTION 
     Examples of the current teachings are disclosed in this application&#39;s text and drawings. The examples advantageously address the long-felt industry needs, as well as other previously unidentified needs, and mitigate shortcomings of the conventional methods and apparatus. Alternate embodiments can be devised without departing from the scope of the invention. Additionally, conventional elements of the current teachings may not be described in detail, or may be omitted, to avoid obscuring aspects of the current teachings. 
     The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. Likewise, the term “embodiments of the invention” does not require that all embodiments of the invention include the discussed feature, advantage, or mode of operation. Use of the terms “in one example,” “an example,” “in one feature,” and/or “a feature” in this specification does not necessarily refer to the same feature and/or example. Furthermore, a particular feature and/or structure can be combined with one or more other features and/or structures. 
     It should be noted that the terms “connected,” “coupled,” or any variant thereof, mean any connection or coupling, either direct or indirect, between two or more elements, and can encompass the presence of one or more intermediate elements between two elements that are “connected” or “coupled” together. The coupling or connection between the elements can be physical, logical, or a combination thereof. As employed herein two elements can be considered to be “connected” or “coupled” together by the use of one or more wires, cables, and/or printed electrical connections, as well as by the use of electromagnetic energy, such as electromagnetic energy having wavelengths in the radio frequency region, the microwave region and/or the optical (both visible and invisible) region, as several non-limiting and non-exhaustive examples. 
     It should be understood that the term “signal” can include any signal such as a data signal, audio signal, video signal, multimedia signal. Information and signals can be represented using any of a variety of different technologies and techniques. For example, data, instructions, process step, commands, information, signals, bits, symbols, and chips that can be referenced throughout this description can be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, and/or any combination thereof. 
     It should be understood that any reference to an element herein using a designation such as “first,” “second,” and so forth does not generally limit the quantity or order of those elements. Rather, these designations can be used herein as a convenient method of distinguishing between two or more elements or instances of an element. Thus, a reference to first and second elements does not mean that only two elements can be employed, or that the first element must necessarily precede the second element. Also, unless stated otherwise, a set of elements can comprise one or more elements. In addition, terminology of the form “at least one of: A, B, or C” used in the description or the claims means “A or B or C or any combination of these elements.” 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising.” “includes,” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     In the following description, certain terminology is used to describe certain features. The term “mobile device” includes, but is not limited to, a mobile phone, a mobile communication device, personal digital assistant, mobile palm-held computer, a wireless device, and/or other types of portable electronic devices typically carried by a person and/or having some form of communication capabilities (e.g., wireless, infrared, short-range radio, etc.). 
     Methods and apparatus for selectively improving integrated circuit performance are provided, in an example, a method is provided that includes defining a critical portion of an integrated circuit layout that determines the speed of an integrated circuit, identifying at least a part of the critical portion that includes at least one of a halo implant region (i.e., a pocket implant), lightly doped drain (LDD), or source drain extension (SDE) implant region, and performing a speed push flow process to increase performance of the part of the critical portion that includes the at least one of the halo, the LDD, and the SDE implant region. 
     The disclosed methods and apparatus improve selected transistors in a chip design to achieve higher performance. The disclosed methods and apparatus provide several advantages. For example, processor performance can be increased significantly higher in a subsequent design than in an original design, without increasing leakage current during a power saving mode. Compared to the conventional circuit redesign approach to improve circuit performance, the disclosed methods and apparatus have nearly zero turnaround time and can be implemented on the fly, while conventional redesigning takes months and consumes expensive engineering resources, Compared to traditional approaches, such as lowering a transistor threshold voltage (Vt) globally (i.e., for the entire integrated circuit), the disclosed methods and apparatus have much lower standby current leakage during the power saving mode, which is a very important feature enhancement for mobile devices. 
       FIG. 1  depicts an exemplary integrated circuit (IC)  100 . The IC  100  has an n-channel transistor (nch) halo implant region  110  and a critical portion  120 . In the example depicted in  FIG. 1 , the critical portion  120  is depicted as a region in the IC  100  that includes a portion of the halo implant region  110 . A region of the IC  100  that is not in the critical portion  120  also includes a portion of the halo implant region  110 . In an example, the halo implant region  110  can include at least one of a lightly doped drain (LDD) implant region and source drain extension (SDE) implant region. The depictions in  FIG. 1  are examples, and are not limiting of the devices and methods described herein. 
     A halo region, such as the halo implant region  110 , is a thin, heavily-doped region of a metal-oxide-silicon field effect transistor (MOSFET) body. The halo region has the same dopant as the MOSFET body, and is located adjacent to the MOSFET&#39;s source-gate and drain-gate junctions. The halo implant is often implanted adjacent to a source drain extension (SDE) implant and/or a lightly doped drain (LDD) implant. The halo region provides a benefit of limiting an extent of depletion regions of the MOSFET&#39;s source-gate and drain-gate junctions, as well as improving the MOSFET&#39;s short-channel behavior. The halo implant also reduces a threshold voltage (Vt) roll-off in short-channel devices. A higher halo implant dose raises the MOSFET&#39;s Vt, which lowers the MOSFET&#39;s performance. In further examples, a region including an LDD and/or a SDE implant region can take the place of the halo implant region  110 . 
     The critical portion  120  is a portion of the IC  100  that determines a limiting speed of the IC  100 . Transistors inside the critical portion  120  can play the most significant role in determining the performance of the IC  100 . The critical portion can be a path in the IC  100  that limits a speed of information flow. Further, the circuits in the critical portion  120  can be capable of powering down during a power-saving mode (e.g., a sleep mode). During the power saving mode, the critical path circuit in the critical portion  120  can be powered down, thus any current leakage in the transistors in the critical portion  120  does not impact leakage-based power loss in the power saving mode. 
     For example, the critical portion  120  can be at least a portion of a processor core. In another example, the critical portion can be at least a portion of an interface circuit (e.g., a network interface, a memory interface, and/or a peripheral interface), at least a portion of a memory, at least a portion of a video display controller, at least a portion of a transmitter, and/or at least a portion of a receiver. 
     Performance of the portion of the critical portion  120  that includes the halo implant region  110  can be selectively improved with a speed push flow process. This region is depicted in  FIG. 1  as being located within both the critical portion  120  and the halo implant region  110 . 
     A speed push flow process is a combination of circuit design and lubrication techniques that improves the performance of a portion of the IC  100 , such as the critical portion  120 . Performance increases can include, and are not limited to, increasing circuit speed and reducing a circuit slew rate. 
     In an example, the critical portion  120  (e.g., critical speed path) of the IC  100  is identified during a design process. Further, a design hold time margin at beyond three-sigma process corners is verified. This guarantees functionality of the IC  100  when a speed of the transistors in the IC  100  is later increased. Next, a design marker layer that covers substantially all transistors in the critical portion  120  is provided. During fabrication, a performance boosting process is performed on selected transistors within the critical portion  120 . There are many ways of boosting circuit performance, such as the speed push flow circuit design and fabrication techniques that are described in each of  FIGS. 2 ,  4 , and  6 A- 6 B. 
       FIG. 2  depicts a typical nch halo implant process  200 . In the typical nch halo implant process  200 , halo implants  205  are fabricated on a substrate  210  with equal doses of do pant. The halo implants  205  are fabricated between a shallow trench implant  215  and a transistor gate  220 . Thus, transistors inside and outside the critical portion  120  have nch halo implants with equivalent doping. 
       FIG. 3  depicts an exemplary nch halo implant speed push flow process  300 . The exemplary nch halo implant speed push flow process  300  can be used to fabricate a p-channel transistor (pch) as well. In the speed push flow process  300 , separate implant masks are created for transistors inside and outside the critical portion  120 . 
     In the nch halo implant speed push flow process  300 , initially, a fabrication process departs from a standard process flow a CMOS process). A first photoresist (PR)  305  is deposited on transistor gates  310  on a substrate  315 . A lithography step is used to pattern the first PR  305  so that the first PR  305  remains outside of the critical portion  120  (i.e., the non-speed push area). Then, a lower implant dose than that used in the standard CMOS flow fabricates first halo implants  320  inside the critical portion  120 . The first halo implants  320  can be fabricated between a shallow trench implant  325  and a transistor gate  310 . Fabricating the first halo implants  320  with a lower implant dose improves performance of the transistors in the critical portion  120  over that of transistors outside the critical portion  120 . This process can be performed for both n-channel transistors and p-channel transistors. Thus, nch transistors and pch transistors in the critical portion  120  have a higher performance (e.g., critical circuit path performance) than devices outside of the critical portion  120 . Next, the first PR  305  is stripped from the regions outside of the critical portion  120 . A second PR layer  330  is deposited on the transistor gates  310  on the substrate  315 . A lithography step patterns the second PR layer  330  so that the second PR layer  330  covers the critical portion  120 . Second halo implants  335  outside the critical portion  120  are fabricated using a typical implant dosage (i.e., a higher dose than that used to fabricate the first halo implants). The second PR layer  330  is then stripped from the critical portion  120 , and the standard CMOS fabrication process continues. 
       FIG. 4  depicts a typical polycrystalline Si gate fabrication process  400 . In the typical polycrystalline Si gate fabrication process  400 , transistor gates  405  inside and outside the critical portion  120 , and on a substrate  410 , are fabricated with the same polycrystalline Si gate (PO) critical dimension (CD). 
       FIG. 5  depicts an exemplary PO CD speed push flow process  500 . In the PO CD speed push flow process  500 , transistors inside and outside the critical portion  120  are fabricated based on different POCD. 
     In the PO CD speed push flow process  500 , initially, the fabrication process departs from the standard CMOS process flow. A dual-CD photo lithography mask is used to pattern a first poly Si gate  505  for devices inside the critical portion  120  and to a pattern a second poly Si gate  510  for devices outside the critical portion  120 . The first poly Si gate  505  and the second poly Si gate  510  are fabricated on a substrate  515 . The dual-CD photo lithography mask has a first portion with a standard PO CD to fabricate devices outside the critical portion  120  (i.e., the non-speed push area), and a second portion with a PO CD smaller than the typical CMOS process to fabricate the devices inside of the critical portion  120  (i.e., the speed push area). This process can be performed for both n-channel transistors (nch) and p-channel transistors (pch), and changes the channel lengths of the nch transistors and the pch transistors. The result is that the transistor channel length for transistors inside critical portion  120  is smaller than that for transistors outside the critical portion, which results iii higher transistor performance inside critical portion  120  than would result if the same CD is used to fabricate transistors both inside and outside the critical portion  120 . After fabrication of the integrated circuit with the dual-CD photo lithography mask, the standard CMOS fabrication processes continue. 
       FIG. 6  depicts a typical gate oxide fabrication process  600 . In the typical gate oxide fabrication process  600 , devices inside and outside the critical portion  120  in the typical integrated circuit are fabricated with a gate oxide  605  having a uniform thickness. The gate oxide  605  is located on a substrate  610 . 
       FIGS. 7A-B  depict an exemplary gate oxide speed push flow process  700 . In the gate oxide speed push flow process  700 , transistors inside and outside the critical portion  120  are fabricated with different gate oxide thicknesses. The speed push flow process  700  uses a first mask to fabricate a thicker gate oxide layer  705  for selected transistors outside the critical portion  120 . A second mask is used, based on a gds marker layerin the critical portion  120 , to fabricate a thinner gate oxide layer  710  (e.g., a TN3 layer) for selected transistors in the critical portion  120 . The thicker gate oxide layer  705  and the thinner gate oxide layer  710  are fabricated on a substrate  715 . 
     Initially, the fabrication process departs from the standard CMOS process flow. A first oxide layer (which forms a transistor gate) is grown for devices both inside the critical portion  120  and outside the critical portion  120 . A photoresist (PR) layer  720  is deposited on the first oxide layer. Then, photolithography is used to pattern the PR layer  720  so that the PR layer  720  covers a portion of the first oxide layer that is outside of the critical portion  120  (i.e., the non-speed push area), and does not cover a portion of the first oxide layer that is inside of the critical portion  120  (i.e., the speed push area). Subsequently, at least a portion of the first oxide layer in the critical portion  120  is removed (e.g., by wet HF etching, etc.), Further, a second oxide layer that is thinner than that of typical process is grown inside the critical portion  120 . As a result of this process, devices in the critical portion  120  have a gate oxide layer that is thinner than devices outside of the critical portion  120 . After fabrication of the first and second oxide layers, the standard CMOS fabrication processes continue. 
       FIGS. 8A-8F  depict exemplary methods for selectively improving integrated circuit performance  800 . The method for selectively improving integrated circuit performance can be performed by the apparatus described hereby, such as a lithographic device configured to perform at least a part of the methods described hereby. In examples, the steps need not necessarily be performed in the order described. 
     In step  802 , a critical portion of an integrated circuit layout that determines the speed of the integrated circuit is defined. In step  804 , at least a part of the critical portion that includes at least one of a halo, lightly doped drain (LDD), and source drain extension (SDE) implant region is identified. In step  806 , a speed push flow process is performed to increase performance of the part of the critical portion that includes the at least one of the halo, the LDD, and the SDE implant region. In optional step  808 , proceed to steps described in  FIGS. 8B-8F . 
     Referring to  FIG. 8B , in step  810 , a first portion of the integrated circuit that includes the halo implant region and is outside the critical portion is masked. In step  812 , a first halo implant is implanted in the portion of the integrated circuit that includes the halo implant region and is inside the critical portion. In step  814 , a second portion of the integrated circuit that includes the halo implant region and is inside the critical portion is masked. In step  816 , a second halo implant in the portion of the integrated circuit that includes the halo implant region and is outside the critical portion is implanted. The second halo implant receives a higher dose of dopant than the first halo implant. 
     Referring to  FIG. 8C , in step  820 , a first portion of the integrated circuit that includes the halo implant region and is outside the critical portion is fabricated. The first portion has first polycrystalline silicon gates having a width based on a first critical dimension. In step  822 , a second portion of the integrated circuit that includes the halo implant region and is inside the critical portion is fabricated. The second portion has second polycrystalline gates having a width based on a second critical dimension. The first critical dimension is greater than the second critical dimension. 
     Referring to  FIG. 8D , in step  830 , a first portion of the integrated circuit that includes the halo implant region and is outside the critical portion is fabricated. The first portion has a first gate oxide layer having a first thickness. In step  832 , a second portion of the integrated circuit that includes the halo implant region and is inside the critical portion second is fabricated. The second portion has a gate oxide layer having a second thickness. The first thickness is greater than the second thickness. 
     Referring to  FIG. 8E , in step  840 , a first portion of the integrated circuit that includes the LDD implant region and is outside the critical portion is fabricated. The first portion has a first dopant concentration. In step  842 , a second portion of the integrated circuit that includes the LDD implant region and is inside the critical portion is fabricated. The second portion has a second dopant concentration. The first dopant concentration is less than the second dopant concentration. 
     Referring to  FIG. 8F , in step  850 , a first portion of the integrated circuit hat includes the SDE implant region and is outside the critical portion is fabricated. The first portion has a first dopant concentration. In step  852 , a second portion of the integrated circuit that includes the SDE implant region and is inside the critical portion is fabricated. The second portion has a second dopant concentration. The first dopant concentration is less than the second dopant concentration. 
     In sonic aspects, the teachings herein can be employed in a mobile device capable of supporting communication. For example, the teachings herein can be applied to a mobile device that is configured to use any one (or combinations) of the following technologies: Code Division Multiple Access (CDMA) systems, Multiple-Carrier) CDMA (MCCDMA), Wideband CDMA (W-CDMA), High-Speed Packet Access (HSPA, HSPA+) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Single-Carrier FDMA (SC-FDMA) systems, Orthogonal Frequency Division Multiple Access (OFDMA) systems, and other multiple access techniques. A mobile device employing the teachings herein can be designed to implement one or more standards, such as IS-95, cdma2000, IS-856, W-CDMA, TDSCDMA, and other standards. A CDMA network can implement a radio technology such as Universal Terrestrial Radio Access (UTRA), cdma2000, or some other technology. UTRA includes W-CDMA and Low Chip Rate (LCR). The cdma2000 technology covers IS-2000, 1S-95 and IS-856 standards. A TDMA network can implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA network can implement a radio technology such as Evolved UTRA (E-UTRA), IEEE 802.11, IEEE 802.16, IEEE 802.20, Flash-OFDM®, etc. UTRA, E-UTRA, and GSM are part of Universal Mobile Telecommunication System (UMTS). The teachings herein can be implemented in a mobile device that is configured to use a 3GPP Lona Term Evolution (LTE) system, an Ultra-Mobile Broadband (UMB) system, and other types of systems LTE is a release of UMTS that uses E-UTRA. UTRA, E-UTRA, GSM, UMTS and LTE are described in documents from an organization named “3rd Generation Partnership Project” (3GPP), while cdma2000 is described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). Although certain aspects of the disclosure can be described using 3GPP terminology, it is to be understood that the teachings herein can be applied to 3GPP (e.g., Re199, Re15, Re16, Re17) technology, as well as 3GPP2 (e.g., 1xRTT, 1xEV-DO RelO, RevA, RevB) technology and other technologies. The techniques can be used in a mobile device that is configured to use emerging and future networks and interfaces. 
     Those of skill in the art will appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described herein generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. 
     Further, many embodiments are described in terms of sequences of actions to be performed by, for example, elements of a computing device. It will be recognized that various actions described herein can be performed by specific circuits (e.g., application specific integrated circuits (ASICs)), by stored program instructions being executed by one or more processors, or by a combination of both. Additionally , the sequence of actions described herein can be embodied entirely within any form of computer-readable storage medium having stored therein a corresponding set of computer instructions that upon execution cause a processor to perform at least a part of the functions described herein. Thus, the various aspects of the invention may be embodied in a number of different forms, all of which have been contemplated to be within the scope of the claimed subject matter. In addition, for each of the embodiments described herein, the corresponding form of any such embodiments may be described herein as, for example, “logic configured to” perform the described action. 
     The disclosed devices and methods can be designed and can be configured into GDSII and GERBER computer files, stored on a computer readable media. These files are in turn provided to fabrication handlers who fabricate devices, based on these files, with a lithographic device. The resulting products are semiconductor wafers that are then cut into semiconductor die and packaged into a semiconductor chip. The chips are then employed in devices described herein. 
     Nothing that is stated or illustrated herein is intended to cause a dedication of any component, step, feature, object, benefit, advantage, or an equivalent to the public, regardless of whether the component, step, feature, object, benefit, advantage, or their equivalent is recited in the claims. While this disclosure describes exemplary embodiments of the invention, it should be noted that various changes and modifications can be made without departing from the scope of the invention as defined by the appended claims.