Semiconductor industry has experienced rapid growth due to continuous improvements in the integration density of a variety of electronic components (e.g., transistors, diodes, resistors, capacitors, etc.). For the most part, this improvement in integration density has come from repeated reductions in minimum feature size, which allows more components to be integrated into a given area.
Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.
The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over, or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” “top,” “bottom” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. Because components in various embodiments can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration only and is in no way limiting. When used in conjunction with layers of an integrated circuit, semiconductor device, or electronic device, the directional terminology is intended to be construed broadly, and therefore should not be interpreted to preclude the presence of one or more intervening layers or other intervening features or elements. Thus, a given layer that is described herein as being formed on, over, or under, or disposed on, over, or under another layer may be separated from the latter layer by one or more additional layers.
While features of integrated circuits shrink, modeling the impact of physical/layout effects up front in integrated circuit designs becomes popular. For integrated circuit designs, process design kits (PDKs) or process access kits (PAKs) have been commercially used to build up the integrated circuits. Generally, PDKs include geometric descriptions and device models of devices, such as transistors, diodes, resistors, capacitors, etc. Circuit design engineers translate PDKs to transistor netlists and/or gate-level netlists for circuit simulations, e.g., Simulation Program with Integrated Circuit Emphasis (SPICE) simulations. Based on the simulation results, circuit design engineers predict and/or modify the designs of the integrated circuits.
Embodiments disclosed herein provide techniques for automatically generating layouts for analog integrated circuits. An integrated circuit is typically constructed using cells, where a cell can contain some or all of a circuit or a component. An analog cell is a cell in which some or all of the cell includes an analog circuit or analog component. In certain embodiments, an analog cell can include one or more parameters that are definable (e.g., parameter values can vary). In some embodiments, an analog cell may have a more unified structure. In one embodiment, some or all of a non-final layout for an integrated circuit is constructed with analog cells.
In the realm of analog design, both power and ground (P/G) alongside the signal can be routing on the front-side of integrated circuits. However, this approach often encounters challenges related to the limited routing area, leading to significant voltage drop issues (IR drop) within the analog circuit. Area penalties on the front side of the integrated circuit lead to the adoption of super power rail (SPR) as a solution. However, the introduction of SPR necessitates careful consideration of how to implement the backside via (VB) and feed-through via (FTV). These components play a crucial role in efficiently connecting different layers and sides of the circuit, ensuring seamless power delivery and signal routing.
In the context of the super power rail (SPR) process, the placement of bumps formed on the back-side of the integrated circuits presents a unique set of challenges. There is a pressing need for a solution proposal to effectively route signals to the backside, ensuring the seamless operation of the analog components. Additionally, the FTV design poses another concern with a high density of cut metal gate (CMG) structures, where the ground rule is often set at about 25%, resulting in CMG densities ranging from about 71% to about 35%. This heightened CMG density introduces process risks that require careful consideration and mitigation strategies.
Furthermore, the SPR process aims to eliminate the constraints imposed by the rule, potentially impacting the overall design and performance of the analog circuits. Therefore, an in-depth impact assessment is crucial to evaluate the consequences and adapt to the evolving requirements of this process.
The present disclosure introduces a new proposal for VB+FTV signal routing to the backside, offering a unique methodology to efficiently route signals in this manner. Additionally, the present disclosure employs dual CMG structures to mitigate the challenges associated with high poly cut (CPO) density. Another innovative aspect involves the redesign of the guard ring (GR) structure, eliminating the rule constraint and resulting in significant area savings of about 3.71% within the analog block.
The advantages and benefits derived from these features are substantial. There is no extra area penalty incurred for inter-cell FTV integration, promoting efficient use of space. Ensuring consistent parasitic resistance (R) for each finger improves mismatch characteristics, enhancing overall performance. Furthermore, the implementation of back-side routing for power, ground, and/or signal connections effectively reduces IR drop concerns, contributing to the robustness and reliability of the analog circuit. This disclosure introduces a super power rail (SPR) analog cell and establishes an auto-migration flow that employs a one-to-one cell mapping approach, ensuring compliance with design rules.
The integrated circuit design system 100 makes it possible to reduce the number of iterations performed during the layout design process by providing a unique and complete design flow that autonomously merges a plural number of device array layouts and generates a CAD layer to enclose the merged device array layouts. The integrated circuit design system 100 also makes it possible to insert dummy patterns around the CAD layer, so as to verify the accuracy of an electrical design or performance of the layout compared to design specifications.
As shown, the integrated circuit design system 100 includes a schematic editor 102, a layout editor 104, a user interface 106, a device array editor 108, and a design rule constraint database 110 that are communicatively coupled to one another. In various embodiments of the present disclosure, the schematic editor 102, the layout editor 104, and the device array editor 108 may each include one or more sets of executable instructions for execution by at least one processor or similar device.
The schematic editor 102 can generate and edit the (e.g., circuit) schematic design of an integrated circuit that is being designed. The schematic editor 102 can perform a pre-layout simulation (e.g., a Simulation Program with Integrated Circuit Emphasis (SPICE) simulation) on the schematic design. According to various embodiments, the schematic editor 102 includes a set of executable instructions for generating or causing the pre-layout simulation of the schematic design. In other embodiments, a separate device (e.g., a simulator) in communication with the schematic editor 102 can generate the pre-layout simulation of the schematic design. The layout editor 104 can generate and edit layouts of the integrated circuits (e.g., device array layouts) in accordance with the schematic design generated by the schematic editor 102. The components of the integrated circuit design system 100 will be discussed in further detail below with respect to the method of
The user interface 106 can receive and display the circuit schematic from the schematic editor 102, the layout from layout editor 104, and any calculated circuit performance parameters. The user interface 106 can receive user inputs to adjust the circuit schematics, the device array layout, and the layout of the integrated circuit, and to select specific devices in order to display circuit performance parameters of specific devices selected by a user.
The method 200 may start with operation 210 of generating the schematic design of an integrated circuit. In various embodiments, the schematic editor 102 can generate the schematic design based on a set of design rule constraints. The schematic editor 102 can query the design rule constraint database 110 for the set of applicable design rules and generate the schematic design of the integrated circuit. The schematic of the integrated circuit may include a plural number of circuit components. The plurality of components may be operatively coupled to one another. At least a first one of the plurality of components can be electrically coupled to a supply voltage. The circuit components may each be represented as a transistor, which can be implemented as an analog cell by the integrated circuit design system 100, for example. In some other embodiments, the circuit component may be implemented as any of various other analog cells, while remaining within the scope of the present disclosure. The schematic of the integrated circuit may also include layout-dependent effect (LDE)-related information of each of the circuit components in a component description format (CDF). The LDE-related information can include dimensions of respective features (e.g., a number of its active regions which may be implemented as fin structures, a channel width, a channel length, a number of gate structures, a gate oxide thickness, etc.) of the circuit component.
In various embodiments, the LDE-related information can include a matching group (MG) of one or more of the circuit components, which may be defined through or otherwise received by the schematic editor 102. Specifically, the matching group may be associated with a corresponding circuit functionality. Such a matching group can be defined by a user of the integrated circuit design system 100. For example, the matching group may include one of: a current mirror, a differential pair, a biasing circuit, a distributed biasing circuit, or a clock sensitive circuit. In some embodiments, the LDE-related information can optionally include the size of a device array layout corresponding to the respective circuit component.
Next, the method 200 may proceed to operation 220 of performing a pre-layout simulation on the schematic design of the integrated circuit. In various embodiments, the schematic editor 102 can simulate the schematic design of the integrated circuit. The pre-layout simulation may be performed on a simulator, such as HSPICE® commercially available from Synopsys, Inc. (San Jose, Calif.), SPECTRE® commercially available from Cadence Design Systems, Inc. (San Jose, Calif.), or any commercially available pre-layout simulator. Upon completion of the pre-layout simulation, a layout of the integrated circuit, including one or more CAD layers that each define the boundary of certain active circuit components, can be generated collectively by the layout editor 104, which will be discussed in detail below.
Further, in various embodiments, the schematic editor 102 can simulate the schematic design with respective scaling factors based on the matching groups of the schematic design. For example, the schematic editor 102 can identify whether each of the circuit components is associated with a respective matching group. If so (i.e., associated with an assigned matching factor), the schematic editor 102 can run the pre-layout simulation (including a Monte Carlo simulation) with a relatively small factor; and if not (i.e., associated with no matching factor), the schematic editor 102 can run the pre-layout simulation (including a Monte Carlo simulation) with a relatively large factor.
Next, the method 200 may proceed to operation 230 of generating and designing a layout for the integrated circuit. In various embodiments, the layout editor 104 can generate the layout based on the schematic design (generated at operation 210) and the pre-simulation result (generated at operation 220). For example, the layout editor 104 can first generate the layout based on the schematic design and the pre-simulation result using a platform, such as VIRTUOSO® commercially available from Cadence Design Systems, Inc. (San Jose, Calif.). The layout may include a plurality of cells that are abutted to one another. Each of the plurality of components may correspond to a respective one of the plurality of cells. Concurrently or subsequently, the layout editor 104 can update, adjust, or otherwise revise the layout by adding an interconnect structure (e.g., super power rails (SPRs)), one or more feed-through vias (FTVs), and/or one or more via structure (VBs), e.g., through operations 232, 234, and 236.
For example, in operation 232, the layout editor 104 may determine a first pattern. The first pattern can be one or more interconnect structure positions. The first pattern can be configured to form an interconnect structure. The interconnect structure can be disposed on a backside of a substate opposite to a frontside of the substate and can carry a supply voltage. In some embodiments, the interconnect structure can be a super power rail (SPR). The SPR may refer to a specialized power distribution network or power rail designed to efficiently deliver power to various components and sections within an integrated circuit.
In operation 234, the layout editor 104 may determine a plurality of second patterns, which will be discussed in further detail with respect to
In operation 236, the layout editor 104 may determine a third pattern, which will be discussed in further detail with respect to
Next, the method 200 may proceed to operation 240 of verifying the layout. In various embodiments, the integrated circuit design system 100 can include a number of verification tools to verify or otherwise check the layout. Examples of such checks include Design Rule Checks (DRCs), Layout-Versus-Schematic (LVS) checks (e.g., layout versus schematic comparison), Layout Parasitic Extraction (LPE) (e.g., a layout parameter extraction for MOS, resistor, capacitors, inductors, and/or other semiconductor devices), Resistance and Capacitance Extraction (RCX) (e.g., interconnect parasitic resistance and capacitance extractions for timing simulations), and other verification steps of checks.
After the layout (or the corresponding schematic design) passes the checks, the method 200 may proceed to operation 250 of performing a post-layout simulation on the schematic design of the integrated circuit. In various embodiments, the schematic editor 102 can simulate the schematic design of the integrated circuit. The post-layout simulation may be performed on a simulator, such as HSPICE® commercially available from Synopsys, Inc. (San Jose, Calif.), SPECTRE® commercially available from Cadence Design Systems, Inc. (San Jose, Calif.), or any commercially available pre-layout simulator.
In the post-layout simulation, various layout-dependent effects are taken into account, so that generated circuit performance parameters reflect the actual circuit more accurately. The circuit performance parameters are then compared to design specification associated with the schematic design. If the circuit performance parameters meet the requirement of the design specification, the schematic design can be approved. Otherwise, the design process reverts back to the schematic generation and editing steps, which include the pre-layout simulation (operation 220), the layout creation (operation 230), the design verification (operation 240), and the post-layout simulation (operation 250) are repeated to modify the schematic design. The process is repeated until the circuit performance parameters meet the requirements of the design specification.
In various embodiments, the method 300 may start at operation 310 in which a schematic of an integrated circuit is received by the layout editor 104. The schematic may include a plurality of components (e.g., transistors) operatively coupled to one another. At least a first one of the plurality of components can be electrically coupled to a supply voltage. The plurality of components can be formed on a frontside of a substrate.
Next, the method 300 may proceed to operation 320 in which a layout can be generated based on the schematic of the integrated circuit by the layout editor 104. The layout may include a plurality of cells that are abutted to one another. Each of the plurality of components may correspond to a respective one of the plurality of cells. In some embodiments, the operation 320 may further determine a first pattern (e.g., BM0). The first pattern can be configured to form an interconnect structure that is disposed on a backside of the substate opposite to the frontside of the substate. The interconnect structure may carry a supply voltage. The interconnect structure may extend along a first lateral direction or a second lateral direction. In some embodiments, the operation 320 may further determine a plurality of second patterns. Each of the plurality of second patterns can be configured to form a first via structure (e.g., via VBs) that electrically couples the supply voltage to one or more of the components. The first via structure may have a first resistance. In some embodiments, the operation 320 may further determine a third pattern. The third pattern can be configured to form a second via structure (e.g., FTV). The second via structure may electrically couple the supply voltage to the one or more of the components. The second via structure may have a second resistance substantially lower than the first resistance.
For example in
In some embodiments, the third pattern 412 (e.g., inter-cell FTV), along the first lateral direction (e.g., X direction), may extend along an edge between the first 402 and second cells 404, as shown in
In some embodiments, the third pattern 412 (e.g., in-cell FTV), along the first lateral direction (e.g., X direction), may extend between the pair of second active regions 408 of the second cell 404, as shown in
VB methodology: In this process, a backside via 702 can be used to establish a direct connection with a source, ensuring that a front-end of line (FEOL) of a non-SPR cell remains unchanged. The key focus here is to re-route power and ground from the backside while keeping the primary functionality intact, as shown in
FTV Methodology: When dealing with a small oxide diffusion (OD) width, FTVs can be seamlessly incorporated through cell-cell mapping, efficiently filling in the available space. For large OD width scenarios, connectivity can be achieved by connecting FTVs through nearby inner guard rings (GR). This approach optimizes FTV placement and routing based on the width of the OD, ensuring efficient signal transmission and power distribution within the SPR analog cells.
In the illustrated embodiment, the analog cell layout 800 may include a filler zone 804. Filler cells (Guard Ring_I) 806, 808, 810, 812, 814 can be inserted into the filler zone 804. Although certain numbers of Guard Ring_C, Guard Ring_V, Guard Ring_H, Active Analog Cell_A, and filler cells (Guard Ring_I) are shown in
In one embodiment, the filler cells 806, 808, 810, 812, 814 can be inserted as a result of a change to the non-final layout. The change can be described in an engineering change order or other document that requests and/or records design changes. Thus, the number and/or placement of the filler cells can change over time (e.g., for each change or for select changes). A filler cell can include one or more components that are included in an active cell, but the component(s) are not used or operating in the filler cell. Alternatively, a filler cell can be an empty area that is devoid of any components.
In some embodiments, the second via structure 412 (e.g., inter-cell FTV), along the first lateral direction (e.g., X direction), may extend along an edge between the first cells 402. In some embodiments, the second via structure 412 (e.g., inter-cell FTV), along the first lateral direction (e.g., X direction), may extend along an edge between the first 402 and second cells 404. In some embodiments, the second cell 404 may form a part of a guard ring for the plurality of components (e.g., transistors).
The layout incorporates the use of feed-through vias (FTV) to connect to the thickened BM0 1704, facilitating an efficient heat dissipation mechanism within the integrated circuit. This design incorporates guidelines for arranging guard rings (GR) in an array, ensuring their proper placement to expand the path of the heat sink. The layout of
In some embodiments, the system 1800 includes an automated place and route (APR) system. In some embodiments, the system 1800 includes a processing device 1802 and a non-transitory, computer-readable storage medium 1804 (“storage device”). The processing device 1802 is any suitable processing device or processing devices. Example processing devices include, but are not limited to, a central processing unit, a microprocessor, a distributed processing system, an application specific integrated circuit, a graphics processing unit, a field programmable gate array, or combinations thereof.
The storage device 1804 may be encoded with or store, for example, computer program code (e.g., a set of executable instructions 1806). Execution of the executable instructions 1806 by the processing device 1802 represents (at least in part) an ECAD tool that implements a portion or all of, the methods described herein to produce the designs for the structures and the ICs disclosed herein. Further, the fabrication tools 1808 may be included for layout and physical implementation of the ICs. In one or more embodiments, the storage device 1804 is a non-transitory electronic, magnetic, optical, electromagnetic, infrared, and/or a semiconductor system (or apparatus or device). For example, the storage device 1804 includes a semiconductor or solid-state memory, a magnetic tape, a removable computer diskette, a random-access memory (RAM), a read-only memory (ROM), a rigid magnetic disk, and/or an optical disk. In one or more embodiments using optical disks, the storage device 1804 includes a compact disk-read only memory (CD-ROM), a compact disk-read/write (CD-R/W), and/or a digital video disc (DVD).
The processing device 1802 is operably connected to the storage device 1804 via a bus 1810. The processing device 1802 is also operably connected to an input/output (I/O) interface 1812 and a network interface 1814 by the bus 1810. The network interface 1814 is operably connected to a network 1816 so that the processing device 1802 and the storage device 1804 are capable of connecting to external elements via the network 1816. In one or more embodiments, the network 1816 is illustrative of any type of wired and/or wireless network, such as an intranet and/or a distributed computing network (e.g., the Internet).
The network interface 1814 allows the system 1800 to communicate with other computing or electronic devices (not shown) via the network 1816. The network interface 1814 includes wireless network interfaces and/or wired network interfaces. Example wireless network interfaces include BLUETOOTH, WIFI, WIMAX, GPRS, or WCDMA. Example wired network interfaces include ETHERNET, USB, or IEEE-1364. In one or more embodiments, some or all of the processes and/or methods disclosed herein are implemented in a distributed system via the network 1816.
The processing device 1802 is configured to execute the executable instructions 1806 encoded in the storage device 1804 to cause the system 1800 to be usable for performing some or all of the processes and/or methods described herein. For example, an electronic design application (e.g., in an ECAD system or as a standalone application) can be configured to perform the methods and techniques shown in
In one or more embodiments, the storage device 1804 stores the executable instructions 1806 configured to cause the system 1800 to be usable for performing some or all of the processes and/or methods. In one or more embodiments, the storage device 1804 also stores information that facilitates execution of a portion of or all of the processes and/or methods. In one or more embodiments, the storage device 1804 stores a cell library 1818 that includes (at least in part) standard and/or previously designed cells.
The I/O interface 1812 is operably connected to I/O devices 1820. In one or more embodiments, the I/O devices 1820 include one or more of an image capture device, a microphone, a scanner, a keyboard, a keypad, a mouse, a trackpad, a touchscreen, and/or cursor direction keys for communicating information and commands to the processing device 1802. The I/O devices 1820 may also include one or more displays, one or more speakers, a printer, headphones, a haptic or tactile feedback device, and the like.
The system 1800 is configured to receive information through the I/O interface 1812. The information received through the I/O interface 1812 includes one or more of instructions, data, design rules, cell libraries, and/or other parameters for processing by the processing device 1802. The information is transferred to the processing device 1802 via the bus 1810. The system 1800 is configured to receive information related to a user interface (UI) through the I/O interface 1812. The information is stored in the storage device 1804 as a UI 1822 or for presentation in the UI 1822.
In some embodiments, a portion or all of the processes and/or methods is implemented as a standalone software application (e.g., an EDA) for execution by a processing device (e.g., processing device 1802). In some embodiments, a portion or all of the processes and/or methods is implemented as a software application that is a part of an additional software application. In some embodiments, a portion or all of the processes and/or methods is implemented as a plug-in to a software application. In some embodiments, at least one of the processes and/or methods is implemented as a software application that is a portion of an EDA tool. In some embodiments, a portion or all of the processes and/or methods is implemented as a software application that is used by the system 1800. In some embodiments, a layout diagram which includes standard and/or previously designed cells is generated using a tool such as VIRTUOSO available from CADENCE DESIGN SYSTEMS, Inc., or another suitable layout generating tool.
In some embodiments, the processes are realized as functions of a program stored in a non-transitory computer readable recording medium (e.g., the storage device 1804). Examples of a non-transitory computer readable recording medium include, but are not limited to, external/removable and/or internal/built-in storage or memory unit, e.g., one or more of an optical disk, such as a DVD, a magnetic disk, such as a hard disk, a semiconductor memory, such as a ROM, a RAM, a memory card, and the like.
As noted above, embodiments of the system 1800 may include the fabrication tools 1808 for implementing the processes and/or methods stored in the storage device 1804. For instance, a synthesis may be performed on a design in which the behavior and/or functions desired from the design are transformed to a functionally equivalent logic gate-level circuit description by matching the design to cells selected from the cell library 1818. The synthesis results in a functionally equivalent logic gate-level circuit description, such as a gate-level netlist. Based on the gate-level netlist, a photolithographic mask may be generated that is used to fabricate the analog integrated circuit by the fabrication tools 1808.
Referring now to
Next, the method 2000 proceeds to operation 2020 of forming a plurality of dummy components each laterally disposed next to one or more of the active components on the frontside of the substrate. The plurality of dummy components are disposed next to the one or more of the active components along a first lateral direction or a second lateral direction. The plurality of dummy components form a part of a guard ring for the plurality of active components.
Next, the method 2000 proceeds to operation 2030 of forming a plurality of first via structures vertically extending through the substate from its backside to the frontside. Each of the first via structures is laterally disposed within a corresponding one of the active or dummy components. The plurality of first via structures are arranged with respect to one another along a tilted direction between the first and second lateral directions. Some of the plurality of first via structures are aligned with one another along the second lateral direction.
Next, the method 2000 proceeds to operation 2040 of forming a second via structure vertically extending through the substate from the backside to the frontside. The second via structure laterally extends within a corresponding one of the dummy components, laterally extends along an edge between one of the active components and one of the dummy components, or laterally extends along an edge between adjacent ones of the active components. In some embodiments, the second via structure, along the first lateral direction, extends along an edge between the first and second cells. In some embodiments, the second via structure, along the first lateral direction, extends between the pair of second active regions of the second cell.
Next, the method 2000 proceeds to operation 2050 of forming a second interconnect structure on the backside of the substrate. The second interconnect structure, coupled to the active components through at least one of the first via structures or the second via structure, is configured to carry a supply voltage for the integrated circuit.
As used herein, the terms “about” and “approximately” generally indicates the value of a given quantity that can vary based on a particular technology node associated with the subject semiconductor device. Based on the particular technology node, the term “about” can indicate a value of a given quantity that varies within, for example, 10-30% of the value (e.g., +10%, +20%, or +30% of the value).
The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.