Exploring VLSI Domains and Skill Sets : Test Chip & CAD Automation

In this episode, we’ll dive into two lesser-known but crucial domains in the VLSI  industry: Test Chip and CAD Automation. These domains don’t receive as much attention as others, such as STA (Static Timing Analysis), Physical Design (PD), or Verification. However, they are indispensable for the seamless functioning and progress of VLSI technology.  

Let’s explore why these domains are essential and how they contribute to the IC design process.  

Why These Domains Are Unique :

Test Chip and CAD Automation domains differ from more popular ones as they:  

• Require a mix of technical, inter-domain knowledge, and management skills.  
• Don’t follow a narrowly focused approach but instead interact with multiple stages of the design process.  
• Play behind-the-scenes roles that are critical for validating and optimizing IC designs.  

So, let’s begin our exploration!  

Test Chip Domain :

The Test Chip domain is fundamental for validating and bench marking the performance of designs, IPs, or innovative technologies.  

What Are Test Chips? 

Test chips, also called prototype chips, are created to ensure the design fulfills its specifications both in simulations (software) and physical silicon (hardware). These chips can include digital, analog, or mixed-signal designs, and even IPs, to evaluate their functionality against key performance metrics.  

Where Test Chip Units Operate in VLSI :

1. ASIC Design Flow:  

• In the RTL to GDS2 flow, SoCs (System on Chips) are designed with multimillion gates.  
• Test chips here are smaller K-chip designs reused across technology nodes and fabrication processes. 

2. Analog Design Flow: 

• Test chips in analog design are smaller, focusing on innovations to improve power, timing, and functionality.  
• These chips validate improvements across technology nodes and new fabrication techniques.  

3. Whole Chip Verification:  

•  A rigorous verification process encompassing analog, digital, and mixed-signal components. 
• Advanced EDA tools and verification techniques are required.  

4. DFT (Design for Testability):  

• Engineers troubleshoot testability issues, bridging gaps between software simulations and silicon validations.  

5. Post-Silicon Validation:  

• Involves hands-on testing of physical chips using advanced lab equipment.  
• Practical knowledge of tools like oscilloscopes and specialized instruments from vendors like Agilent is essential.  

6. Silicon Reporting:  

• The final step, where software-to-silicon results are compared and compiled into detailed reports for customers.  
• This is a high-responsibility role, requiring years of experience.  

CAD Automation Domain :

Computer-Aided Design (CAD) Automation ensures seamless tool integration and workflow efficiency across the VLSI design process.  

What Is CAD Automation?  

CAD engineers develop and maintain automation frameworks to support various design stages. These frameworks optimize time and resources, allowing designers to focus on creating innovative chips.  

Subdomains in CAD Automation:  

1. Frontend CAD:  

•  Covers RTL to synthesis and schematic design flows.  
•  Requires understanding of EDA tools and continuous updates to automate bug fixes and enhancements.  

2. DFT CAD:  

• Focuses on automation for smooth DFT inspections and testing.  

3. PNR (Place and Route) CAD:  

• Automates layout mechanisms for both digital and analog designs.  
• Requires knowledge of TCL scripting and proprietary languages like SKILL.  

4. Physical Verification CAD:  

•  Handles DRC (Design Rule Check), LVS (Layout vs. Schematic), and EMIR (Electromigration and IR drop) checks.  
•  Requires expertise in tools like ICV, PVS, and Calibre.  

5. IP View CAD:  

• Maintains consistency across multiple views of IPs, ensuring compatibility with various EDA tools and foundry requirements.  

6. Design Environment CAD:  

•  Develops user-friendly interfaces (GUIs) that streamline design workflows, saving designers significant time.  

 Core Skills for CAD Engineers : 

• Scripting Knowledge: Proficiency in scripting languages such as Python, Perl, TCL, and Bash.  
• Version Control: Familiarity with systems like CVS or SVN for managing automation repositories.  
• Resource Management: Expertise in tools like Univa Grid Engine (UGE) or IBM Load Sharing Facility (LSF) for computational resource optimization.  
• Communication and Troubleshooting: Cross-team collaboration and problem-solving skills are critical in resolving complex design challenges.  

Conclusion :

Both Test Chip and CAD Automation are pivotal to the VLSI industry’s progress. While these domains might not always be in the spotlight, they are integral to ensuring design accuracy, efficiency, and innovation.  

We hope this episode sheds light on these hidden gems of VLSI and helps you explore potential career paths in these exciting fields.  

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Exploring VLSI Domains and Skill Sets: IP Design & Characterization

In this episode, we’ll dive into the types of IPs (Intellectual Property) used in the VLSI domain and explore what makes this field so crucial in modern electronics. If you’re curious about how technology progresses and evolves, this is an episode you won’t want to miss. Let’s get started!

What is IP in VLSI?

In the world of VLSI, IP (Intellectual Property) refers to a self-contained design block with clearly defined inputs and outputs, capable of performing a specific function. The idea behind IP is simple: design once, reuse multiple times. This approach speeds up the development process and ensures consistency across projects.

What is Characterization?

Characterization in VLSI is the process of analyzing and recording the electrical properties of an IP (such as current, voltage, power variations, etc.) under different conditions. This step ensures the IP functions reliably across a range of environments and applications.

Types of IPs in VLSI:

Here’s a look at the major types of IPs designed in the VLSI domain:

1. Standard Cell IPs

These are the building blocks of any digital design, such as an ASIC or SoC. Standard cell libraries include:

• Logic cells (e.g., AND, OR gates)
• Sequential cells (e.g., flip-flops, latches)
• Power management cells
• Special cells (e.g., filler cells, decap cells)

Standard cell characterization is a key focus area, as variations in PVT (Process, Voltage, and Temperature) and threshold voltage impact their performance.

2. Memory IPs

Memory is integral to modern devices. Common types include:

• SRAM (Static RAM)
• DRAM (Dynamic RAM)
• NVM (Non-Volatile Memory), such as Flash
• BRAM (Battery-Backed RAM)

Memory IPs are designed at two levels:

• Unit Memory Cell Design
• Memory Array Design

Characterization ensures reliable storage and retrieval of data under varying conditions.

3. Analog IPs

These IPs perform specific analog functions and are critical in applications like power management, audio, and signal generation. Examples include:

• DC-DC Converters
• Phase-Locked Loops (PLLs)
• Audio IPs

4. SerDes IPs

SerDes (Serializer/Deserializer) IPs convert parallel data to serial and back, enabling high-speed data transfer in modern devices. They are particularly popular in handheld gadgets.

5. Mixed Signal IPs (e.g., USB, MIPI, PHY)

Mixed signal IPs, such as USB, MIPI, and PHY, bridge the analog and digital worlds. With the rise of plug-and-play devices, these IPs are in high demand.

6. IO Pad IPs

IO Pads manage the interface between the silicon chip and external circuitry. These are essential in any chip design.

Design Views and Skill Sets in IP Characterization

At the core of IP design and characterization lies the need for highly specialized skill sets. Here’s a breakdown:

1. HDL Representation

For digital IPs, you’ll use:

• Verilog/System Verilog
• VHDL

For analog IPs:

• Verilog-A
• Verilog-AMS

2. Timing Library Characterization

This involves performing dynamic timing analysis to record parameters like:

• Delay
• Slew
• Rise/Fall times

Tools: Liberate, Silicon Smart  

Format: Liberty (.lib)

3. Layout Design:

Layouts are handcrafted at the unit cell level, where components like diffusion layers, poly, and metal layers are meticulously designed.

Tools: Virtuoso, Custom Compiler  

Free Option: Magic Layout

4. Parasitic Extraction

Extracting parasitic resistance and capacitance ensures accurate simulation of the physical design. Tools like StarRC or QRC are used for this purpose.

5. Physical Verification

Tools like Calibre, ICV, and PVS are used for:

• DRC (Design Rule Checks)
• LVS (Layout vs. Schematic)
• EM/IR Checks

6. Schematic Design

For analog IPs, schematic design involves:

• Interconnecting components (active and passive)
• Simulating using AC, DC, or transient analysis

Free Tool: LTSpice

The Evolution of IP Design:

As technology advances, the need for innovative IPs grows. The scaling of technology nodes, increasing device complexity, and new applications in AI, IoT, and high-speed computing have spurred the creation of novel IPs.

The IP design and characterization field promises a future rich with opportunities for skilled professionals.

Conclusion:

The IP Design and Characterization domain is the backbone of VLSI innovation. Whether you're drawn to standard cells, memory, analog, or mixed-signal IPs, each offers a unique blend of challenges and rewards.

Thanks for reading! See you soon!

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Exploring VLSI Domains and Skill Sets: Analog & Analog Mixed Signal (AMS)

In this episode, we delve into two fascinating VLSI domains: Analog Design and Analog Mixed Signal (AMS) Design. While their names might sound similar, these domains require distinctly different skill sets. If you're curious about the differences and the expertise needed for each, stick around until the end!

Setting the Stage:

This episode is part of our ongoing series answering a question from our viewer. As previously mentioned, the detailed answer spans multiple episodes. In this second installment, we'll be focusing on the Analog Design and AMS Design domains. Let's get started!

Domains Inside Analog Design:

Analog design is rooted in concepts many of you may have encountered during your college days. If you've worked with SPICE or explored circuits like operational amplifiers (op-amps), phase-locked loops (PLLs), or oscillators, you're already on familiar ground.

Let's break down the key aspects:

1.Schematic Design :  

• Why It Matters: In the industry, manual SPICE-based node labeling isn't practical for complex designs. Instead, schematic capture tools like Cadence Virtuoso and Synopsys Custom Compiler streamline the process. These tools provide graphical interfaces to design and simulate circuits efficiently.  
• Skills Needed:  
• Strong foundation in analog electronics.  
• Familiarity with schematic capture tools like Virtuoso and LTspice (a free option to start with).  
• Knowledge of analysis methods such as transient, AC, DC, and noise analysis.  

2. Layout Design  

• Process: Analog layout design often employs semi-custom or full-custom techniques, particularly for unique blocks. Tools like Virtuoso and Custom Compiler are essential for this stage.  
• Skills Needed:  Expertise in analog layout methodologies.   Ability to optimize for performance metrics like noise, power and parasitics.  

3. Physical Verification  

• Verification Steps:  
• Using tools like Calibre DRC, LVS, and ICV to ensure design rule compliance and layout correctness.  
• DSPF Extraction with tools like StarRC to check parasitic effects.  
• Running EMIR (Electromigration and IR drop) checks and making necessary corrections.  
• Skills Needed:  
• Mastery of verification tools and scripting languages like Tcl for custom rule coding.  

4. Post-Layout Functional Verification  

• Objective: Incorporating parasitic effects into the design and ensuring performance remains within permissible limits.  
• Tools Used: Industry-standard SPICE simulators like HSPICE, Spectre, and CustomSim for efficient simulations.  

Domains Inside AMS Design:

AMS design combines analog and digital blocks, leveraging the best of both worlds. The scaling down of technology nodes below 10nm has made AMS designs increasingly relevant.

1. System-Level Modeling  

• Approach: Design begins with a top-down or bottom-up methodology. Tools like C++, Simulink, and SystemVerilog are used for system-level modeling.  
• Skills Needed: Proficiency in system-level modeling and simulation tools.  

2. Behavioral Design  

• Analog Behavioral Modeling:  
• Verilog-A is used for analog components.  
• Verilog-AMS allows seamless integration of analog and digital components.  
• Digital Behavioral Modeling: Verilog or SystemVerilog.  
• Skills Needed: Expertise in Verilog, Verilog-A, and Verilog-AMS.  

3. Mixed-Signal Verification  

• Process:  Concurrent simulation of analog and digital blocks using SPICE (for analog) and Verilog (for digital).  Proper configuration of A-to-D and D-to-A converters to facilitate smooth signal transactions.  
• Tools Used: Virtuoso AMS, CustomSim AMS, and Vista IDMS simulators.  

4. AMS Layout and Physical Verification  

• Layout Tools: AMS-specific layout capabilities in tools like Virtuoso AMS and Custom Compiler AMS Layout.  
• Verification: Standard DRC, LVS, ERC checks, and EMIR analysis.  
• Additional Skills:  
• Coding DRC rules with Tcl or tool-specific languages.  
• Deep understanding of silicon fabrication processes.  

Conclusion:

The Analog and AMS domains offer exciting opportunities, but they require dedicated learning and practice. From foundational tools like SPICE to advanced simulators like HSPICE and Virtuoso AMS, mastering these skills can open doors to rewarding VLSI careers.  

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Exploring VLSI Domains and Skill Sets: ASIC & FPGA

 

In this, we’ll explore the various domains in VLSI (Very Large Scale Integration) where you can build a career. Additionally, we’ll break down the specific skill sets needed for each domain. This topic stems from a viewer's request to clarify what professionals do in different VLSI domains like design, verification, and physical design. 

Since this is a broad topic, we’re dividing it into multiple posts. This blog is part one, so stay tuned for future installments!

Introduction to VLSI Domains: A Bird's Eye View

The VLSI ecosystem is vast and can be broadly divided into several domains:

1. Digital Design:

Digital design caters to various chip technologies like ASIC (Application-Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), and SoC (System-on-Chip).  The digital design flow typically starts with RTL (Register Transfer Level) coding and ends with a GDSII (Graphic Data System) file for fabrication.

2. Analog Design :

In analog design, engineers work on components like PLLs (Phase-Locked Loops), op-amps, and oscillators. These components are crucial for circuits that process analog signals.

3. Analog Mixed-Signal (AMS) Design

AMS design combines analog and digital techniques, widely used in technologies like USB, SerDes, and IP cores. This domain bridges the gap between digital and analog design.

4. IP Design and Characterization :

IP (Intellectual Property) design involves creating reusable design blocks, such as:

• Digital IP: Logic gates, sequential elements.
• Analog IP: Converters (ADC/DAC), PLLs, memory cells.

5. Test Chip Development :

Test chips are prototypes that test designs on actual silicon. They validate performance by comparing test outcomes with simulation results, providing critical feedback for final production.

6. CAD and Automation :

CAD (Computer-Aided Design) automation tools form the backbone of all VLSI domains. Proficiency in these tools is essential across the board.

Domains Within Digital Design:

Let’s dive deeper into digital design, which spans multiple specialized domains:

1. RTL Design :

•  What It Entails: Writing hardware description languages (HDLs) like Verilog, VHDL, or SystemVerilog to define the chip’s behavior.
• Skills Needed: 
•  Advanced expertise in HDLs.
•  Strong problem-solving skills to design complex circuits.

2. Verification :

• What It Entails: Ensuring the chip design meets its specifications through methodologies like UVM (Universal Verification Methodology) and OVM (Open Verification Methodology).
• Skills Needed: 
• System Verilog assertions.
• Knowledge of LRMs (Language Reference Manuals) to stay updated with industry changes.

3. DFT (Design for Testability) : 

• What It Entails: Designing chips with built-in testing features for post-manufacturing validation.
• Skills Needed: Familiarity with tools like Tetramax and concepts like ATPG (Automatic Test Pattern Generation), BIST (Built-In Self-Test), and JTAG (Joint Test Action Group).

4. Physical Design :

• What It Entails: Translating RTL designs into layouts for fabrication. This stage includes:
• PNR (Place and Route).
• CTS (Clock Tree Synthesis).
• ECO (Engineering Change Order).
• Skills Needed: Tools like Cadence Encounter or Synopsys ICC2.

5. Physical Verification

• What It Entails: Verifying the layout with checks like:
• DRC (Design Rule Check).
• LVS (Layout vs. Schematic).
• ERC (Electrical Rule Check).
• Skills Needed: Tools such as IC Validator and PERC.

6. STA (Static Timing Analysis)

• What It Entails: Analyzing timing paths to ensure designs meet speed and performance goals.
• Skills Needed: Mastery of tools like PrimeTime and ETS

 7. Sign-Off :

• What It Entails: Finalizing the design for tape-out (fabrication). Engineers in this domain require comprehensive knowledge of the RTL-to-GDSII flow.
• Skills Needed: Tools like LEC (Logical Equivalence Check) and IREM.

Final Thoughts:

Each VLSI domain offers unique challenges and opportunities. While large companies often have specialized teams for each domain, startups may require engineers to handle multiple responsibilities. The choice of domain depends on your interest and expertise.

Stay tuned for upcoming blogs where we’ll discuss analog design, AMS design, and other key domains in detail. 

Let’s simplify VLSI, one domain at a time. Until next time, happy learning! 😊

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