Saturday, September 13, 2008

Full ASIC Design Flow

As an ASIC Engineer, we should have idea about the whole ASIC design and verification flow. Here I have described all the useful steps which must be follow start from the thinking of the Micro architecture to the Fabrication of the Chip.

I hope this information will be useful as an ASIC Engineer. Please leave your comments or question if you have any. I will try my best to reply you soon.

Step 1: Create an Micro-Architecture Document.

Step 2: RTL Design & Development of IP's

Step 3: Functional verification all the IP's/Check whether the RTL is free from Linting Errors/Analyze whether the RTL is Synthesis friendly.
Step 3a: Perform Cycle-based verification(Functional) to verify the protocol behaviour of the RTL
Step 3b: Perform Property Checking , to verify the RTL implementation and the specification understanding is matching.

Step 4: Prepare the Design Constraints file (clock definitions(frequency/uncertainity/jitter),I/O delay definitions, Output pad load definition, Design False/Multicycle-paths) to perform Synthesis, usually called as an SDC synopsys_constraints, specific to synopsys synthesis Tool (design-compiler)

Step 5: To Perform Synthesis for the IP, the inputs to the tool are (library file(for which synthesis needs to be targeted for, which has the functional/timing information available for the standard-cell library and the wire-load models for the wires based on the fanout length of the connectivity), RTL files and the Design Constraint files, So that the Synthesis tool can perform the synthesis of the RTL files and map and optimize to meet the design-constraints requirements. After performing synthesis, as a part of the synthesis flow, need to build scan-chain connectivity based on the DFT(Design for Test) requirement, the synthesis tool (Test-compiler), builds the scan-chain.

6: Check whether the Design is meeting the requirements (Functional/Timing/Area/Power/DFT) after synthesis.
Step 6a: Perform the Netlist-level Power Analysis, to know whether the design is meeting the power targets.
Step 6b: Perform Gate-level Simulation with the Synthesized Netlist to check whether the design is meeting the functional requirements.
Step 6c: Perform Formal-verification between RTL vs Synthesized Netlist to confirm that the synthesis Tool has not altered the functionality.
Step 6d: Perform STA(Static Timing Analysis) with the SDF(Standard Delay Format) file and synthesized netlist file, to check whether the Design is meeting the timing-requirements.
Step 6e: Perform Scan-Tracing , in the DFT tool, to check whether the scan-chain is built based on the DFT requirement.

Step 7: Once the synthesis is performed the synthesized netlist file(VHDL/Verilog format) and the SDC (constraints file) is passed as input files to the Placement and Routing Tool to perform the back-end Actitivities.

Step 8: The next step is the Floor-planning, which means placing the IP's based on the connectivity,placing the memories, Create the Pad-ring, placing the Pads(Signal/power/transfer-cells(to switch voltage domains/Corner pads(proper accessibility for Package routing), meeting the SSN requirements(Simultaneous Switching Noise) that when the high-speed bus is switching that it doesn't create any noise related acitivities, creating an optimised floorplan, where the design meets the utilization targets of the chip.
Step 8a : Release the floor-planned information to the package team, to perform the package feasibility analysis for the pad-ring .
Step 8b: To the placement tool, rows are cut, blockages are created where the tool is prevented from placing the cells, then the physical placement of the cells is performed based on the timing/area requirements.The power-grid is built to meet the power-target's of the Chip .

Step 9: The next step is to perform the Routing., at first the Global routing and Detailed routing, meeting the DRC(Design Rule Check) requirement as per the fabrication requirement.

Step 10: After performing Routing then the routed Verilog netlist, standard-cells LEF/DEF file is taken to the Extraction tool (to extract the parasitics(RLC) values of the chip in the SPEF format(Standard parasitics Exchange Format), and the SPEF file is generated.

Step 11: Check whether the Design is meeting the requirements (Functional/Timing/Area/Power/DFT/DRC/LVS/ERC/ESD/SI/IR-Drop) after Placement and Routing step.
Step 11a: Perform the Routed Netlist-level Power Analysis, to know whether the design has met the power targets.
Step 11b: Perform Gate-level Simulation with the routed Netlist to check whether the design is meeting the functional requirement .
Step 11c: Perform Formal-verification between RTL vs routed Netlist to confirm that the place & route Tool has not altered the functionality.
Step 11d: Perform STA(Static Timing Analysis) with the SPEF file and routed netlist file, to check whether the Design is meeting the timing-requirements.
Step 11e: Perform Scan-Tracing , in the DFT tool, to check whether the scan-chain is built based on the DFT requirement, Peform the Fault-coverage with the DFT tool and Generate the ATPG test-vectors.
Step 11f: Convert the ATPG test-vector to a tester understandable format(WGL)
Step 11g: Perform DRC(Design Rule Check) verfication called as Physical-verification, to confirm that the design is meeting the Fabrication requirements.
Step 11h: Perform LVS(layout vs Spice) check, a part of the verification which takes a routed netlist converts to spice (call it SPICE-R) and convert the Synthesized netlist(call it SPICE-S) and compare that the two are matching.
Step 11i : Perform the ERC(Electrical Rule Checking) check, to know that the design is meeting the ERC requirement.
Step 11j: Perform the ESD Check, so that the proper back-to-back diodes are placed and proper guarding is there in case if we have both analog and digital portions in our Chip. We have seperate Power and Grounds for both Digital and Analog Portions, to reduce the Substrate-noise.
Step 11k: Perform seperate STA(Static Timing Analysis) , to verify that the Signal-integrity of our Chip. To perform this to the STA tool, the routed netlist and SPEF file(parasitics including coupling capacitances values), are fed to the tool. This check is important as the signal-integrity effect can cause cross-talk delay and cross-talk noise effects, and hinder in the functionality/timing aspects of the design.
Step 11l: Perform IR Drop analysis, that the Power-grid is so robust enough to with-stand the static and dynamic power-drops with in the design and the IR-drop is with-in the target limits.

Step 12: Once the routed design is verified for the design constraints, then now the next step is chip-finishing activities (like metal-slotting, placing de-coupling caps).

Step 13: Now the Chip Design is ready to go to the Fabrication unit, release files which the fab can understand, GDS file.

Step 14: After the GDS file is released , perform the LAPO check so that the database released to the fab is correct.

Step 15: Perform the Package wire-bonding, which connects the chip to the Package.

7 comments:

Jaydip Mehta said...

Step 1 ??

Ankit Gopani said...

Hi Jaydeep,

First of all thanks to visit my blog everyday...

Regarding first step. It should be the idea and thinking on the architecute (That is obviouse and must). Any way I have modified steps sequence. Hope you have read this blog and find it useful.

-Ankit

mital said...

Hi Ankit,
Thats a brilliant effort..!!

I guess lot of people dont know about ASIC and your blog provides a great insight.

Ankit Gopani said...

Hi Mital,

Thanks for reading my blog regularly.

Actually the idea is to share some ASIC knowledge with full of funn in Gujarati. So ASIC Engineers like you and in our filed gets full fun with ASIC knowledge.

-Ankit

Mayda said...

Good for people to know.

Jay Panchal said...

Hey... The first step should be design architecture and not micro-architecture... The micro-architecture means the detailed design level information that the designer document after coding their design...!

Ankit Gopani said...

Hey Jay,
Thanks for your input.

I think that all depend on the CMMI level process. In some small projects design guys are come with architecture as well as detailed microlevel description.
But you are right Jay, this is not the process as per the CMMI level 3. So first step should be design architecture not the microlevel architecure.

Thanks for your input. Keep reading and provide your inputs.