Abstract:
An integrated circuit device comprising a memory cell array including a plurality of memory cells wherein each memory cell includes at least one electrically floating body transistor having source, drain and a body regions, wherein the body region is electrically floating and disposed between the source and drain regions; a gate is disposed over the body region. Each memory cell includes a first data state representative of a first charge in the body region and a second data state representative of a second charge in the body region. The integrated circuit device further includes operating characteristics adjustment circuitry, coupled to the memory cell array, to adjust one or more operating or response characteristics of one or more memory cells to improve the uniformity of operation/response characteristics of the memory cells of the memory cell array relative to the other memory cells of the array.

Description:
RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application Ser. No. 60/626,745, entitled “Method of Improving Statistical Distribution of IC and IC Implementing Same”, filed Nov. 10, 2004. The contents of this provisional application are incorporated by reference herein in their entirety. 
    
    
     BACKGROUND 
     In one aspect, the inventions relate to a semiconductor memory cell, array, and device, and techniques for improving, enhancing and/or controlling variations of operating and/or response parameter(s) or characteristic(s) of the memory cell, array and/or device; and more particularly, in one aspect, to improving, enhancing and/or controlling variations of such parameter(s) or characteristic(s) of the semiconductor dynamic random access memory (“DRAM”) cell, array and/or device wherein the memory cell(s) includes an electrically floating body in which an electrical charge is stored. 
     Briefly, there is a continuing trend to employ and/or fabricate advanced integrated circuits using techniques, materials and devices that improve performance, reduce leakage current and enhance overall scaling. However, scaling down of transistor sizes often leads to increase of variations of the operating and/or response characteristics. These variations or mismatch tend to have a significant impact on precision integrated circuit (“IC”) design. Indeed, due to variations or mismatch, IC designers, such as DRAM designers, typically include substantial design margin or risk yield loss, both of which adversely affect speed, efficiency and production costs. 
     One type of dynamic random access memory cell is based on, among other things, a floating body effect of Silicon-on-Insulator (“SOI”) transistors. (See, for example, U.S. patent application Ser. No. 10/450,238, Fazan et al., filed Jun. 10, 2003 and entitled “Semiconductor Device”, hereinafter “Semiconductor Memory Device Patent Application”). In this regard, the memory cell may consist of a PD or a FD SOI transistor (or transistor formed in bulk material/substrate) on having a channel, which is disposed adjacent to the body and separated therefrom by a gate dielectric. The body region of the transistor is electrically floating in view of the insulation or non-conductive region (for example, in bulk-type material/substrate) disposed beneath the body region. The state of memory cell is determined by the concentration of charge within the body region of the SOI transistor. 
     Such an electrically floating body memory cell has at least two current states corresponding to different logic states, for example, a logic high or State “1” and a logic low or State “0”. With reference to  FIGS. 1A ,  1 B and  1 C, in one embodiment, semiconductor DRAM device  10  includes a plurality of memory cells  12 , arranged in an array  10   a,  wherein each memory cell  12  includes transistor  14  having gate  16 , body region  18 , which is electrically floating, source region  20  and drain region  22 . The body region  18  is disposed between source region  20  and drain region  22 . Moreover, body region  18  is disposed on or above region  24 , which may be an insulation region (for example, in SOI material/substrate) or non-conductive region (for example, in bulk-type material). The insulation or non-conductive region is disposed on substrate  26 . 
     Notably, the entire contents of the Semiconductor Memory Device Patent Application, including, for example, the features, attributes, architectures, configurations, materials, techniques and advantages described and illustrated therein, are incorporated by reference herein. SOI is a material in which such devices may be fabricated on or in (hereinafter collectively “on”). Such devices are known as SOI devices and include, for example, partially depleted (PD), fully depleted (FD) devices, multiple gate devices (for example, double or triple gate), and Fin-FET. SOI devices have demonstrated improved performance (for example, speed), reduced leakage current characteristics and considerable enhancement in scaling. 
     Data is written into or read from a selected memory cell by applying suitable control signals to a selected word line(s)  28 , a selected source line(s)  30  and/or a selected bit line(s)  32 . In response, charge carriers are accumulated in or emitted and/or ejected from electrically floating body region  18  wherein the data states are defined by the amount of carriers within electrically floating body region  18 . As mentioned above, memory cell  12  of DRAM array  10  operates by accumulating majority carriers (electrons or holes)  34  in, or emitting/ejecting majority carriers  34  from body region  18  of, for example, N-channel transistors. (See,  FIGS. 2A and 2B ). In this regard, accumulating majority carriers (in this example, “holes”)  34  in body region  18  of memory cells  12  via, for example, impact ionization near source region  20  and/or drain region  22 , is representative of a logic high or State “1”. (See,  FIG. 2A ). Emitting or ejecting majority carriers  30  from body region  18  via, for example, forward biasing the source/body junction and/or the drain/body junction, is representative of a logic low or State “0”. (See,  FIG. 2B ). 
     Reading is performed by comparison of a cell current with the current from a reference cell that is usually placed between the State “1” and State “0”. Several techniques may be implemented to read the data stored in (or write the data into) memory cells  12  of DRAM device  10 . For example, a current sense amplifier (not illustrated) may be employed to read the data stored in memory cells  12 . In this regard, a current sense amplifier may compare the cell current to a reference current, for example, the current of a reference cell (not illustrated). From that comparison, it may be determined whether memory cell  12  contained a logic high (relatively more majority carries  34  contained within body region  18 ) or logic low data state (relatively less majority carries  28  contained within body region  18 ). 
     For at least the purposes of this discussion, logic high or State “1” corresponds to an increased concentration of majority carries in the body region relative to a non-programmed device and/or a device that is programmed with a logic low or State “0”. In contrast, logic low or State “0” corresponds to a reduced concentration of majority carries in the body region relative to a non-programmed device and/or a device that is programmed with a logic high or State “1 ”. 
     A sufficiently large statistical variation in the device characteristics (for example, device currents) may cause or lead to an erroneous reading of the data state stored in the device. (See,  FIG. 3 ). In contrast, a narrow statistical variation in the device characteristics tends to enhance uniformity of operation and performance of the devices. This provides greater confidence that the data stored in the memory device is correctly read during a read operation. 
     While electrically floating body transistors of memory cells (for example, SOI transistors) are highly scalable, variations or mismatch of transistor characteristics result in IC designers incorporating significant design margin to enhance or maximize yield. There is a need for ICs (for example, ICs that include electrically floating body transistors of memory cells) that incorporate circuitry and/or techniques that address variations or mismatch of transistor characteristics. In this way, IC designers may eliminate the need for substantial design margin or risk yield loss, which may adversely affect speed, efficiency and production costs. 
     SUMMARY OF THE INVENTIONS 
     There are many inventions described and illustrated herein. The present inventions are neither limited to any single aspect nor embodiment thereof, nor to any combinations and/or permutations of such aspects and/or embodiments. Moreover, each of the aspects of the present inventions, and/or embodiments thereof, may be employed alone or in combination with one or more of the other aspects of the present inventions and/or embodiments thereof. For the sake of brevity, many of those permutations and combinations will not be discussed separately herein. 
     In one aspect, the present inventions are directed to an integrated circuit device comprising a memory array including a plurality of memory cells wherein each memory cell includes at least one electrically floating body transistor having a source region, a drain region, a body region disposed between the source region and the drain region, wherein the body region is electrically floating and a gate disposed over the body region and separated therefrom by a gate dielectric. Each memory cell includes a first data state representative of a first charge in the body region and a second data state representative of a second charge in the body region wherein the second charge is substantially provided by removing charge from the body region through the gate. The integrated circuit device further includes operating characteristics adjustment circuitry, coupled to the memory cell array, to responsively adjust one or more operating or response characteristics of one or more predetermined memory cells and thereby enhance the uniformity of operation or response of the predetermined memory cells of the memory array relative to the plurality of memory cells of the memory array. 
     In one embodiment, the operating characteristics adjustment circuitry adjusts one or more operating or response characteristics of one or more predetermined memory cells by applying a bias to one or more of the word line, source line and/or bit line associated with the one or more predetermined memory cells. 
     In another embodiment, the operating characteristics adjustment circuitry adjusts one or more operating or response characteristics of one or more predetermined memory cells by applying a threshold voltage shift in the one or more predetermined memory cells. 
     In yet another embodiment, the operating characteristics adjustment circuitry adjusts one or more operating or response characteristics of one or more predetermined memory cells by adjusting the reference voltage applied to the sense amplifier which is associated with the one or more predetermined memory cells. 
     The integrated circuit device of this aspect of the inventions may also include control logic, coupled to the operating characteristics adjustment circuitry, to control the operating characteristics adjustment circuitry to adjust one or more operating or response characteristics of one or more predetermined memory cells and thereby enhance the uniformity of operation or response of the predetermined memory cells of the memory array relative to the plurality of memory cells of the memory array. 
     In another aspect, the present inventions are directed to a system comprising a first integrated circuit device including memory array including a plurality of memory cells wherein each memory cell includes at least one electrically floating body transistor having a source region, a drain region, a body region disposed between the source region and the drain region, wherein the body region is electrically floating, and a gate disposed over the body region and separated therefrom by a gate dielectric. The memory cells include a first data state representative of a first charge in the body region and a second data state representative of a second charge in the body region, wherein the second charge is substantially provided by removing charge from the body region through the gate. The first integrated circuit device also includes operating characteristics adjustment circuitry, coupled to the memory cell array, to responsively adjust one or more operating or response characteristics of one or more predetermined memory cells and thereby enhance the uniformity of operation or response of the plurality of memory cells of the memory array. 
     The system further includes a bus and a second integrated circuit device including control logic, coupled to the operating characteristics adjustment circuitry via the bus, to control the operating characteristics adjustment circuitry to adjust one or more operating or response characteristics of one or more predetermined memory cells and thereby enhance the uniformity of operation or response of the predetermined memory cells of the memory array relative to the plurality of memory cells of the memory array. 
     In one embodiment of this aspect of the inventions, the operating characteristics adjustment circuitry adjusts one or more operating or response characteristics of one or more predetermined memory cells by applying a bias to one or more of the word line, source line and/or bit line associated with the one or more predetermined memory cells. In another embodiment, the operating characteristics adjustment circuitry adjusts one or more operating or response characteristics of one or more predetermined memory cells by applying a threshold voltage shift in the one or more predetermined memory cells. In yet another embodiment, the operating characteristics adjustment circuitry adjusts one or more operating or response characteristics of one or more predetermined memory cells by adjusting the reference voltage applied to the sense amplifier which is associated with the one or more predetermined memory cells. 
     In one embodiment, the control logic of the second integrated circuit enables the operating characteristics adjustment circuitry to adjust one or more operating or response characteristics of one or more predetermined memory cells and thereby enhance the uniformity of operation or response of the plurality of memory cells of the memory array based on at least the amount of time the first integrated circuit device has been in operation or deployed. 
     In another aspect, the present inventions are directed to a method of operating an integrated circuit device comprising a memory array including a plurality of memory cells having a state, and operating characteristics adjustment circuitry, coupled to the memory cell array, to responsively adjust one or more operating or response characteristics of one or more predetermined memory cells and thereby enhance the uniformity of operation or response of the plurality of memory cells of the memory array. The method comprises applying control signals to the memory cells, via associated word, source and/or bit lines, to read the data state of the memory cells, and applying a bias voltage to the word line, source line and/or bit line associated with the one or more predetermined memory cells to enhance the uniformity of operation or response of the predetermined memory cells relative to the plurality of memory cells of the memory array. 
     In one embodiment, each memory cell includes at least one electrically floating body transistor having a source region, a drain region, a body region disposed between the source region and the drain region, wherein the body region is electrically floating and a gate disposed over the body region and separated therefrom by a gate dielectric. The memory cell includes a first data state representative of a first charge in the body region, and a second data state representative of a second charge in the body region, wherein the second charge is substantially provided by removing charge from the body region through the gate. The method of this embodiment further includes applying a threshold voltage shift in the one or more predetermined memory cells via applying a bias voltage to the word line, source line and/or bit line associated with the one or more predetermined memory cells. 
     In another embodiment, each memory cell includes a floating gate and the method further includes adjusting the floating gate charge for the predetermined memory cells to enhance the uniformity of operation or response of the predetermined memory cells relative to the plurality of memory cells of the memory array. 
     Again, there are many inventions, and aspects of the inventions, described and illustrated herein. This Summary of the Inventions is not exhaustive of the scope of the present inventions. Moreover, this Summary of the Inventions is not intended to be limiting of the inventions and should not be interpreted in that manner. While certain embodiments have been described and/or outlined in this Summary of the Inventions, it should be understood that the present inventions are not limited to such embodiments, description and/or outline, nor are the claims limited in such a manner. Indeed, many others embodiments, which may be different from and/or similar to, the embodiments presented in this Summary, will be apparent from the description, illustrations and claims, which follow. In addition, although various features, attributes and advantages have been described in this Summary of the Inventions and/or are apparent in light thereof, it should be understood that such features, attributes and advantages are not required whether in one, some or all of the embodiments of the present inventions and, indeed, need not be present in any of the embodiments of the present inventions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the course of the detailed description to follow, reference will be made to the attached drawings. These drawings show different aspects of the present inventions and, where appropriate, reference numerals illustrating like structures, components, materials and/or elements in different figures are labeled similarly. It is understood that various combinations of the structures, components, materials and/or elements, other than those specifically shown, are contemplated and are within the scope of the present inventions. 
         FIG. 1A  is a schematic representation of a prior art semiconductor DRAM array including a plurality of memory cells comprised of one electrically floating body transistor; 
         FIG. 1B  is a three dimensional view of an exemplary prior art memory cell comprised of one electrically floating body transistor (PD-SOI NMOS); 
         FIG. 1C  is a cross-sectional view of the prior art memory cell of  FIG. 1B , cross-sectioned along line C-C′; 
         FIGS. 2A and 2B  are exemplary schematic illustrations of the charge relationship, for a given data state, of the floating body, source and drain regions of a prior art memory cell comprised of one electrically floating body transistor (PD-SOI NMOS); 
         FIG. 3  illustrates statistical variations in the currents read from an electrically floating body transistor; 
         FIGS. 4A and 4B  are schematic representations of exemplary memory devices, including an array of electrically floating body transistors and operating characteristics adjustment circuitry, in accordance with certain aspects of the present inventions; 
         FIG. 5  is a graphical illustration of a threshold voltage shift, in accordance with an exemplary embodiment of the present inventions, induced by applying predetermined voltages to the gate and drain of a MOSFET arranged in an exemplary memory array; 
         FIG. 6  is a graphical illustration of improved distributions after proposed adjustment in accordance with aspects of the technique of the present inventions; and 
         FIGS. 7A-7C  are schematic representations of exemplary architectures and/or embodiment of implementing a controller/processor in conjunction with memory devices having operating characteristics adjustment circuitry, in accordance with the present inventions. 
     
    
    
     DETAILED DESCRIPTION 
     At the outset, it should be noted that there are many inventions described herein as well as many aspects and embodiments of those inventions. 
     In a first aspect, the present inventions are directed to circuitry and techniques for improving, enhancing and/or controlling variations of operating and/or response characteristic(s) of integrated circuits or circuit devices, for example, memory cells, arrays and/or devices. In one embodiment, the techniques employ an input (for example, electrical bias, light, heat and control signal) to change the operating and/or response characteristic(s) of the integrated circuit and/or transistors therein, for example, memory cell, array and device. In this way, variations of operating and/or response characteristic(s) may be controlled, enhanced and/or improved; thereby reducing, eliminating and/or minimizing statistical variations in the device characteristics (for examples device currents). As mentioned above, a narrow statistical variation in the device characteristics tends to enhance uniformity of operation and performance of the devices, which leads to greater confidence that the data stored in the memory device is correctly read during, for example, a read operation. 
     With reference to  FIG. 4A , in one embodiment, exemplary memory device  10  includes a memory array  10   a,  having a plurality of memory cells  12  (see, for example,  FIGS. 1A-2B ), and operating characteristics adjustment circuitry  36 . In one embodiment, operating characteristics adjustment circuitry  36  receives a command generated in device  10  and, in response thereto, adjusts the operating and/or response characteristic(s) of memory cell  12 , array  10   a  and/or device  10 . In another embodiment, operating characteristics adjustment circuitry  36  receives an external command on bus or signal lines  38  and responsively adjusts the operating and/or response characteristic(s) of memory cell  12 , memory array  10   a  and/or memory device  10 . 
     For example, where memory cell  12  is comprised of electrically floating body transistors  14 , as described above, sufficiently biasing one or more, or predetermined word lines  28 , source lines  30 , and/or bit lines  32  of memory array  10   a  may adjust the operating and/or response characteristic(s) of the corresponding memory cells  12  of memory device  10 . In this regard, data states “1” and “0” of one or more, all, or predetermined memory cells  12  (for example, those connected to the biased word lines  28 , source lines  30 , and bit lines  32 ) may be adjusted, fine tuned or “tweaked” so that the operating and/or response characteristic(s) of those memory cells  12  is more uniform relative to other memory cells  12  of memory array  10   a.  The application of the bias to word lines  28 , source lines  30  and/or bit lines  32  (see, for example,  FIGS. 1A-2B ) may provide a threshold voltage shift in those selected or predetermined memory cells  12  thereby causing a change in the read current. (See,  FIG. 5 ). 
     In another embodiment, operating characteristics adjustment circuitry  36  adjusts the reference voltage which may be employed by a sense amplifier to sense the data state of one, some, all or predetermined memory cells  12  of memory array  10   a. In this way, operating characteristics adjustment circuitry  36  improves uniformity of operation and performance of memory cell  12 , memory array  10   a  and/or memory device  10 , which leads to greater confidence that the data stored in the memory device is correctly read during, for example, a read operation. 
     As mentioned above, in one embodiment, a command or control signals may be externally provided to memory device  10  via bus  38 . The input/output circuitry  40  may thereafter provide the command or control signals to operating characteristics adjustment circuitry  36  (based on, for example, analysis of the command/control signals by control logic, for example, a state machine (not illustrated)). In response, circuitry  36  may implement one or more adjustment, fine tuning or “tweaking” operations. In one embodiment, the type or form of such operations may be determined by the particular command/control signals (i.e., the control signal selects the type or form of operation). In another embodiment, the control signal initiates one type or form of operation. 
     Notably, in one embodiment, the adjustment, fine tuning or “tweaking” of the operating and/or response characteristic(s) of one or more, all or predetermined memory cells  12  may be implemented by inducing a specific amount of fixed charge into the gate dielectric of memory cell(s)  12  via application of the bias to word lines  28 , source lines  30  and/or bit lines  32 . To facilitate this process, initial traps may be induced into the gate dielectric during fabrication. 
     Floating gate devices, like EEPROM or Flash, provide an additional opportunity for the adjustment. In this case, the device parameters adjustment may be implemented by adjusting, controlling and/or changing the floating gate charge. 
     Notably, the adjustment, fine tuning or “tweaking” operations in different types of integrated circuit devices may be implemented by electrical modifications as well as, for example, light and radiation. 
     With reference to  FIG. 6 , after adjustment, fine tuning or “tweaking” of the operating and/or response characteristic(s) of the given memory cells  12 , the distributions of State “1” and State “0” are more uniform. This may provide higher confidence and greater reliability in correctly reading the data stored in memory cell  12  and/or memory device  10 . 
     The adjustment of the operating and/or response characteristic(s) of the memory cell  12 , array  10   a  and/or device  10  may be performed during manufacture (immediately prior to or after packaging), during test and/or in the field, for example, by a controller/processor after device  10  has aged or undergone stress. In those instances where the adjustment is performed in the field (i.e., when deployed in, for example, a system), control signals to engage or enable the on-chip operating characteristics adjustment circuitry  36  (and the adjustment, fine tuning or “tweaking” operations performed thereby), may be provided by control logic  42  resident on memory device  10  and/or via an external controller/processor. (See,  FIG. 4B ). 
     In particular, with continued reference to  FIG. 4B , in another exemplary embodiment, memory device  10  includes control logic  42  to enable, control or engage operating characteristics adjustment circuitry  36  to adjust the operation of memory device  10 . In one embodiment, the resident control logic  42  may employ external control signals and/or internal data of the response or operation of device  10  to control certain parameters (for example, the threshold voltages of the memory cells and/or the reference voltages of selected circuitry). In this way, memory device  10  may be adjust, correct and/or control certain parameters to accommodate and/or compensate for changes in the operating conditions of predetermined memory cells  12  and/or memory device  10 . The control logic  42 , in one embodiment, may employ a look-up table and/or a predetermined or mathematical relationship to adjust and/or control the operating and/or response characteristic(s) of all or predetermined memory cells  12  and/or memory device  10 . 
     With reference to  FIGS. 7A-7C , the control logic  42  may be implemented in external controller/processor  44 . External controller/processor  44  may be implemented on module  100  (see, for example,  FIG. 7A ), in system  1000  having a distributed bus architecture (see, for example,  FIG. 7B ), and/or in system  1000  having a point-point architecture (see, for example,  FIG. 7C ). In each embodiment, controller/processor  44  may provide control signals to memory device  10  which, in response, enables or engages the resident operating characteristics adjustment circuitry  36 . 
     In one embodiment, controller/processor  44  may perform an algorithm to determine the operating margins of memory device  10  in order to determine whether to implement the adjustment, fine tuning or “tweaking” operations for memory device  10 . In another embodiment, controller/processor  44  may instruct operating characteristics adjustment circuitry  36  to implement the adjustment, fine tuning or “tweaking” operations based on the amount of time memory device  10  has been in operation or deployed in the field. Indeed, controller/processor  44  may employ any type of algorithm or techniques, whether now known or later developed, to determine whether to implement the adjustment, fine tuning or “tweaking” operations for memory device  10 . 
     There are many inventions described and illustrated herein. While certain embodiments, features, attributes and advantages of the inventions have been described and illustrated, it should be understood that many others, as well as different and/or similar embodiments, features, attributes and advantages of the present inventions, are apparent from the description and illustrations. As such, the embodiments, features, attributes and advantages of the inventions described and illustrated herein are not exhaustive, and it should be understood that such other, similar, as well as different, embodiments, features, attributes and advantages of the present inventions are within the scope of the present inventions. 
     For example, while a considerable portion of the inventions was described in the context of a memory device, memory cell and/or memory array, the present inventions may be implemented in any integrated circuit and/or integrated circuit transistor. 
     As mentioned above, each of the aspects of the present inventions, and/or embodiments thereof, may be employed alone or in combination with one or more of such aspects and/or embodiments. For the sake of brevity, those permutations and combinations will not be discussed separately herein. As such, the present inventions are neither limited to any single aspect (nor embodiment thereof), nor to any combinations and/or permutations of such aspects and/or embodiments. 
     Moreover, the above embodiments of the present inventions are merely exemplary embodiments. They are not intended to be exhaustive or to limit the inventions to the precise forms, techniques, materials and/or configurations disclosed. Many modifications and variations are possible in light of the above teaching. It is to be understood that other embodiments may be utilized and operational changes may be made without departing from the scope of the present inventions. As such, the foregoing description of the exemplary embodiments of the inventions has been presented for the purposes of illustration and description. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the inventions not be limited solely to the description above.