This disclosure relates generally to memory cells, and more specifically, but not exclusively, to antifuse based memory cells.
Silicon-on-insulator (SOI) devices use a layered silicon-insulator-silicon substrate structure as opposed to the more conventional bulk silicon substrate typically used in semiconductor manufacturing. In general, an SOI device consists of a semiconductor substrate on which a thin insulating layer, usually made of silicon dioxide and referred to as the “buried oxide” or “BOX,” layer is formed, e.g., by implantation of oxygen into the bulk silicon substrate. An active region of silicon is formed on the BOX layer. The active silicon layer includes circuit elements of an integrated circuit (IC), e.g., transistors and diodes.
One advantage of isolating the circuitry of the active layer from the bulk semiconductor substrate using the buried oxide layer is a decrease in parasitic capacitance, which improves performance, e.g., provides increased device speed and reduced power usage. Because of these advantages, SOI structures are desirable for high frequency applications such as radio frequency (RF) communication circuits.
In a conventional SOI structure, the SOI structure includes a substrate layer, an insulator layer (BOX), and an active layer. The substrate layer is typically a semiconductor material such as silicon. The insulator layer is a dielectric which is often silicon dioxide formed through the oxidation of a portion of the substrate layer where the substrate layer is silicon. The active layer includes an active device layer and a metallization or metal interconnect layer. The active layer further includes a combination of dopants, dielectrics, polysilicon, metal wiring, passivation, and other layers, materials or components that are present after circuitry has been formed therein. The circuitry may include metal wiring (e.g. in the metal interconnect layer), passive devices such as resistors, capacitors, and inductors, and active devices such as a transistor (e.g., in the active device layer). One issue that may arise with SOI devices is relatively high leakage in the devices of the active layer. In order to compensate for such leakage, a higher threshold voltage (Vt) may be necessary. However, a high Vt may limit the devices' performance and speed.
High volume programmable read only memory (PROM) is needed in RF applications to enable programming of parts to customer needs, tune modules, and improve yields. Existing solutions include poly fuses, but they take a very large area, and antifuses. However, conventional antifuses have certain drawbacks. For example, use of a passgate transistor in the antifuse may allow the leakage from the pass gate to raise the voltage at node A (node between the passgate and antifuse) and will cause the antifuse capacitor to fail. In another example, a transistor is used as the antifuse to bypass this issue. However, this option enables the source of the antifuse transistor at node B (node after antifuse) to pull down the voltage of node A when it is not being programmed. Alternatively, a second transistor may be used as a protection device for the antifuse capacitor. This reduces the leakage and creates a capacitive voltage division. As a result, when the Bitline (BL) is pulsed, there is less of a high transient voltage on the antifuse.
Accordingly, there is a need for systems, apparatus, and methods that overcome the deficiencies of conventional approaches including the methods, system and apparatus provided hereby.
The following presents a simplified summary relating to one or more aspects and/or examples associated with the apparatus and methods disclosed herein. As such, the following summary should not be considered an extensive overview relating to all contemplated aspects and/or examples, nor should the following summary be regarded to identify key or critical elements relating to all contemplated aspects and/or examples or to delineate the scope associated with any particular aspect and/or example. Accordingly, the following summary has the sole purpose to present certain concepts relating to one or more aspects and/or examples relating to the apparatus and methods disclosed herein in a simplified form to precede the detailed description presented below.
In one aspect, a memory device comprises: an oxide layer; a pass transistor on a front side of the oxide layer; an antifuse device on the front side of the oxide layer proximate to the pass transistor; a pass transistor gate on a backside of the oxide layer; and an antifuse gate on the front side of the oxide layer.
In another aspect, a memory device comprises: an oxide layer; means for switching a signal on a front side of the oxide layer; means for creating a conductive path on the front side of the oxide layer proximate to the means for switching; a pass transistor gate on a backside of the oxide layer; and an antifuse gate on the front side of the oxide layer.
In still another aspect, a memory device comprises: a pass transistor on a first portion of the memory device; an antifuse device on a second portion of the memory device opposite the first portion; a pass transistor gate on a back side of the memory device; an antifuse gate on a front side of the memory device opposite the backside side; and a bias gate on the back side of the memory device proximate to the pass transistor gate.
In still another aspect, a memory device comprises: means for switching a signal on a first portion of the memory device; means for creating a conductive path on a second portion of the memory device opposite the first portion; a pass transistor gate on a back side of the memory device; an antifuse gate on a front side of the memory device opposite the back side; and means for biasing on the back side of the memory device proximate to the pass transistor gate.
Other features and advantages associated with the apparatus and methods disclosed herein will be apparent to those skilled in the art based on the accompanying drawings and detailed description.
A more complete appreciation of aspects of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings which are presented solely for illustration and not limitation of the disclosure, and in which:
In accordance with common practice, 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.
The exemplary methods, apparatus, and systems disclosed herein mitigate shortcomings of the conventional methods, apparatus, and systems, as well as other previously unidentified needs. In some examples, a backside metal layer is used as the passgate transistor gate in a memory device. This will ensure that the passgate dielectric can handle more than 10V ensuring the ability to use a high voltage on BL and better damage to the antifuse gate dielectric and more simplified layout and bias circuitry. In other examples, a backside bias is used to ensure the antifuse is protected. The use of a backside pass gate may increase the threshold voltage (Vt) and reduce the leakage that could result in unintended programming. In addition, the use of an antifuse protection bias, similar to a write support bias, creates a field that increases the potential in the antifuse body and protects the antifuse along with providing a smaller solution than conventional approaches. In still other examples, the use of a backside contact to form an antifuse removes that need for a pass gate creating a very small antifuse cell with simplified layout and bias circuitry. It should be understood that a metal backside or gate structure described herein may be composed of polysilicon, copper, tungsten, aluminum, cobalt, or other similar material.
In a write operation, the antifuse cell 100 may have an initial condition with all sources and nodes at ground voltage. In the next stage, setup, the antifuse cell 100 may impose 5 v on the source 175 for the passgate (BL, the passgate transistor 110 will have a thick enough second dielectric layer 150 to handle the 5 v). Then, in the programming phase, the antifuse cell 100 may impose a pulse of 5-10 v on the passgate gate 165 to breakdown the first dielectric layer 140 and program the antifuse cell 100. In a read operation, a bias voltage of approximately 1.2 v (Vcore, typical system voltage) may be imposed on the antifuse gate 145. Then the current from the antifuse source 135 may be measured to determine the value of the cell. For example, if no current then the cell 100 is a zero. If a current is detected, the cell 100 is a one.
It will be appreciated that various aspects disclosed herein can be described as functional equivalents to the structures, materials and/or devices described and/or recognized by those skilled in the art. For example, in one aspect, an apparatus may comprise means for performing the functions of the antifuses described herein. In another example, a memory device (e.g., antifuse cell 100, antifuse cell 300, antifuse cell 400, and antifuse cell 700) comprising: an oxide layer (e.g., oxide layer 130, oxide layer 330, oxide layer 430, and oxide layer 730); means for switching a signal (e.g. passgate transistor 110, passgate transistor 310, passgate transistor 410, and passgate transistor 710) on a front side of the oxide layer; means for creating a conductive path (e.g. antifuse device 120, antifuse device 320, antifuse device 420, and antifuse device 710) on the front side of the oxide layer proximate to the means for switching; a pass transistor gate (e.g. passgate gate 165, passgate gate 365, passgate gate 465, and passgate gate 765) on a backside of the oxide layer; and an antifuse gate (e.g. antifuse gate 145, antifuse gate 345, antifuse gate 445, antifuse gate 745) on the front side of the oxide layer.
In still another example, a memory device (e.g., antifuse cell 100, antifuse cell 300, antifuse cell 400, and antifuse cell 700) may comprise: means for switching a signal (e.g. passgate transistor 110, passgate transistor 310, passgate transistor 410, and passgate transistor 710) on a first portion of the memory device; means for creating a conductive path (e.g. antifuse device 120, antifuse device 320, antifuse device 420, and antifuse device 710) on a second portion of the memory device opposite the first portion; a pass transistor gate (e.g. passgate gate 165, passgate gate 365, passgate gate 465, and passgate gate 765) on a back side of the memory device; an antifuse gate (e.g. antifuse gate 145, antifuse gate 345, antifuse gate 445, antifuse gate 745) on a front side of the memory device opposite the back side; and means for biasing (e.g., protection bias 364, protection bias 464, and protection bias 764) on the back side of the memory device proximate to the pass transistor gate. It will be appreciated that the aforementioned aspects are merely provided as examples and the various aspects claimed are not limited to the specific references and/or illustrations cited as examples.
One or more of the components, processes, features, and/or functions illustrated in
The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any details described herein as “exemplary” is not to be construed as advantageous over other examples. Likewise, the term “examples” does not mean that all examples include the discussed feature, advantage or mode of operation. Furthermore, a particular feature and/or structure can be combined with one or more other features and/or structures. Moreover, at least a portion of the apparatus described hereby can be configured to perform at least a portion of a method described hereby.
The terminology used herein is for the purpose of describing particular examples and is not intended to be limiting of examples of the disclosure. 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, actions, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, actions, operations, elements, components, and/or groups thereof.
It should be noted that the terms “connected,” “coupled,” or any variant thereof, mean any connection or coupling, either direct or indirect, between elements, and can encompass a presence of an intermediate element between two elements that are “connected” or “coupled” together via the intermediate element.
Any reference herein to an element using a designation such as “first,” “second,” and so forth does not limit the quantity and/or order of those elements. Rather, these designations are used as a convenient method of distinguishing between two or more elements and/or instances of an element. Also, unless stated otherwise, a set of elements can comprise one or more elements.
Those skilled in the art will appreciate that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof
Nothing stated or illustrated depicted in this application is intended to dedicate any component, action, feature, benefit, advantage, or equivalent to the public, regardless of whether the component, action, feature, benefit, advantage, or the equivalent is recited in the claims.
Although some aspects have been described in connection with a device, it goes without saying that these aspects also constitute a description of the corresponding method, and so a block or a component of a device should also be understood as a corresponding method action or as a feature of a method action. Analogously thereto, aspects described in connection with or as a method action also constitute a description of a corresponding block or detail or feature of a corresponding device. Some or all of the method actions can be performed by a hardware apparatus (or using a hardware apparatus), such as, for example, a microprocessor, a programmable computer or an electronic circuit. In some examples, some or a plurality of the most important method actions can be performed by such an apparatus.
In the detailed description above it can be seen that different features are grouped together in examples. This manner of disclosure should not be understood as an intention that the claimed examples have more features than are explicitly mentioned in the respective claim. Rather, the disclosure may include fewer than all features of an individual example disclosed. Therefore, the following claims should hereby be deemed to be incorporated in the description, wherein each claim by itself can stand as a separate example. Although each claim by itself can stand as a separate example, it should be noted that-although a dependent claim can refer in the claims to a specific combination with one or a plurality of claims-other examples can also encompass or include a combination of said dependent claim with the subject matter of any other dependent claim or a combination of any feature with other dependent and independent claims. Such combinations are proposed herein, unless it is explicitly expressed that a specific combination is not intended. Furthermore, it is also intended that features of a claim can be included in any other independent claim, even if said claim is not directly dependent on the independent claim.
Furthermore, in some examples, an individual action can be subdivided into a plurality of sub-actions or contain a plurality of sub-actions. Such sub-actions can be contained in the disclosure of the individual action and be part of the disclosure of the individual action.
While the foregoing disclosure shows illustrative examples of the disclosure, it should be noted that various changes and modifications could be made herein without departing from the scope of the disclosure as defined by the appended claims. The functions and/or actions of the method claims in accordance with the examples of the disclosure described herein need not be performed in any particular order. Additionally, well- known elements will not be described in detail or may be omitted so as to not obscure the relevant details of the aspects and examples disclosed herein. Furthermore, although elements of the disclosure may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated.
The present Application for Patent claims the benefit of Provisional Application No. 62/793,856 entitled “ANTIFUSE MEMORY CELLS” filed Jan. 17, 2019, assigned to the assignee hereof, and expressly incorporated herein by reference in its entirety.
Number | Date | Country | |
---|---|---|---|
62793856 | Jan 2019 | US |