ST MICROELECTRONICS

1. Fast, efficient and scalable multi-corner SoC Signoff analysis extension with programmable in-situ Spice level analysis capability ST MICROELECTRONICS Anjali Supekar *, Mohita Batra *, Rakesh Gulati *, Shahabuddin Qureshi °, Hina Mushir#, Prashant Pandey#, Samant Paul °, Seema Jaiswal ° * Automation Team ° IP Team # Silicon Test and Debug Team

2. Due to reduced margins in the SOC design, number of critical path are increasing. • Digital timing analysis methods are shaking hands with spice validation methodologies resulting in mixed signal analysis modes. • CURRENT METHODS: • Highly time consuming • Use complete spice (large size) However….. • OUR INTEND: • Simulating any path of any hierarchy of a design • Quick & flexible analysis of true behavior of the path over wide range of operating conditions • Use output of the tool to optimize the design .

3. STA Mixed Mode Multiple corner butTime Taking Limited corner Huge pattern set Less Accurate Unable to characterize small portion of hard IP Large coverage(Not specific, unsuitable for flat design) With change in technologies, there was a need to reduce the “extra margin” under consideration in order to get characterization for a small area leading to more optimistic approach. With the existing options (Sign Off /Mixed Mode) , analysis was possible only at full block level and hierarchical analysis was not supported. For such huge hierarchies we have developed a solution which lies between HDL and mixed mode analysis . The solution provides extraction at multiple corners and increased accuracy

4. APPLICATION UNDER STUDY: CAD CORRECTION FACTOR Q Slope Clock Slope • Expected Access Time on Silicon: TA • Actual Access Time obtained from CAD: TAA • CAD Correction Factor (CCF) Δ = TA - TAA • TA =Δ + TAA Source Clock Memory Q1 LSB 1 Load Clock • Total Contribution (4-1) • Balancing Contribution (2-1) • Path Contribution ( 4-3) • PulseGen Contribution (3-2) Q2 MSB 4 2 3 Pulse Generator Sensor Pulse Clock Pulse Propagation CK & Q PULSE FROM MEM CCF

5. PROBLEM STATEMENT: • The TAAmeasured on chip measurement (Sensor) is going below CAD fast limits. • CAD analysis on TAApulse propagation from memory to Sensor shows reduction in pulse width Test chip logic for pulse propagation And mixing to a central location Central Location (Pulse To digital Conversion) CUT1 Memory Q PULSEGEN (Sensor lib) CK Sensor -Balanced structure (Controlled placement and routing etc) CUTn Memory Digital Output Q PULSEGEN (Sensor lib) CK Pulse variation Error depends on input Slopes. Error of the order of medium size inverter delay Error sources in TAAmeasurement TERROR-TC : Rise (Edge) Delay – Fall (Edge) Delay This value (extracted from STA) is provided in testdoc on signoff conditions for each cut

6. CCF TOOL FLOW SimulationEnvironment LoadSlopes XLS Clock Slopes XLS Spice Simulator Detailed CCF

7. The PVT Generator is an automation tool written in VB which facilitates the generation of PVT sheet from the standard input sources from the Front End and Sensor data INPUTS • Memory Test Specification • Clock SlopeDelivered along with SPICE files • PVT Mapping Information • Simulation and Spice Extraction Temperature • Process and RC Extraction

8. PVT GENERATOR FLOW

9. CCF Flow involves parsing of PVT Topsheet which contains CUT details and PVT information for CCF calculations. • For Spice simulation, it processes Spice to be directly used, write simulation stubs for each cut, to calculate Clock slopes and CCF. • Simulation Environment : Automation supports, Writing simulation files and invoking Simulation Environment for launching of clock slope simulations and CCF simulations. • Flow supports Compilation of the Clock slopes and CCF for all the CUTs in tool internal format

10. Manual (Before Automation) After Automation User need not be aware of any simulation tools. Tool is user friendly and no prior knowledge required. Set-up Time reduced to half an hour Parallel simulation along with tracking mechanism. At any point user can check simulation status of any CUT. Simulation time reduced to 4-5 hours Result compilation made easy with proper monitoring of all sheets for each cut. Time reduced to 5-6 minutes Easy Debug options • Thorough knowledge about Spice files, its extraction, modification, Eldo simulation and other tools for calculating CCF • Set-up Time was approximately 1-2 days (includes spice extraction, correction, run files, stimuli and other data files) • Simulation was initially sequential. Even if it was parallel, there was no tracking mechanism. Simulation time was approximately 4-5 days • Result compilation was tedious as there were many excel sheets having huge data which was unmanageable. It took approximately 8-10 hours • No debug options 90% of user time is saved

11. CAD CORRECTION FACTOR T1 T2 T3 T4 T5 SYSTEM ACCURACY PURE MEMORY CAD V5 > V1 T5<T1 NEW MEMORY CAD CAD v/s Silicon Analysis of a Testchip V1 V2 V3 V4 V5 CAD v/s SI Aligned with Increased Accuracy of new CCF

12. MOTIVATION ENHANCEMENTS PotentialApplications Proposed solution addresses different components of SOC. • Process Sensor Block (for Sensor Data Analysis) • Temperature sensitivity • voltage sensitivity • RC Impact • Impact of device sensitivity CAD Correction Factor (CCF) + MCF (Memory) A TAA error value calculation for test chips is an important step to calculate path contribution to extract the deviation of CAD from Silicon. Testchip Process Sensor Memory Ring Oscillators • Standard Cell RO Block CAD Data • Generation for any type of architecture (flops, mux, etc) • easy analysis (currents, timing , frequency)

13. EXISTING FLOWNEW OPTIMIZED FLOW Clock Slope / load @ multiple corners • AUTOMATIC CAD CORRECTION FACTOR GENERATION THROUGH MCF Extract Load slopes @ multiple corners Clock Slope and Q load @ multiple corners Extract memory CAD Extract slope @ multiple corners simulations for Unified CAD Data {CCF included} TESTCHIP TEAM manual adjustment for CCF Extracts CCF @ multiple corners CAD Data Delivery Memory team do delivery of CAD Data to Test team TESTCHIP TEAM MEMORY TEAM 3X Gain MEMORY TEAM Cycle time + No. of simulations 13 " Faster & Accurate" CAD data generation for Improving Accuracy for CAD vs Si analysis.

14. Process Sensor Block Tool fully automates the Sensor Design Analysis and CAD Data Generation for Silicon validation. Voltage Sensitivity Sensor Data Analysis RC Impact Temperature Sensitivity

15. Enable this tool for SoC designers at physical implementation stage. • Option for generating GDS and CDL of a specific portion of targeted block of SOC taking DEF as input and then extracting Spice from GDS and CDL. • Analyzing Critical paths using Actual Spice Simulations