Technology

What to know about Integrated Circuit Design Flow

A small electronic circuit, also known as an integrated circuit, chip, or microchip, is created on the surface of thin semiconductor material. It can be found in practically all modern electronic devices, including computers, microwaves, phones, and other digital appliances. It is separated into three types: digital, analogue, and mixed-signal. Digital chips are tiny, fast, have low power loss, and are inexpensive. Because they work by processing continuous signals, analogue ICs can make circuit design easier. Mixed-signal chips integrate digital and analogue circuits on a single chip to perform functions adequately; they are smaller in size and cost less, but signal interference must be carefully considered.

IC Design Flow

Chip design is a complicated process that needs years of study and hands-on experience to master. Digital integrated circuit design hierarchy or phases include.

  • System design,
  • Logic design,
  • Circuit design,
  • Layout design,
  • Fabrication, and
  • Testing.

These procedures are not necessarily in any particular order; interactions are practiced in order to get things done correctly.

System Design

This stage specifies the chip’s specifications and primary functions. While defining these criteria, it considers issues such as chip area, power, functionality, speed, cost, and other design aspects. During this stage, the designer’s resources may become a constraint. For example, a designer might want to develop a semiconductor that works at 1.2V, but current process technology can only support 5V. In this case, the designer must modify the specs to accommodate the available tools. Before designing and specifying a system, it’s always a good idea to familiarize yourself with the available process technology. Process technology refers to the regulations that govern the fabrication of a chip in a certain foundry. AMI 0.5um, TSMC 0.35um, and IBM 0.13um are some examples. A design based on a single process technology is unique to that process and should be produced in a foundry that supports that technology. The major aspects of the system are depicted with diagrams at the design level, and no details are mentioned on the blocks. Only the sections’ input and output characteristics are specified.

Logic Design

The designer implements the logic networks that will materialize the input and output features defined in the previous step at this level. This is typically made up of logic gates with interconnecting wires to implement the concept. This is important in Probe Card Manufacturing.

Circuit Design

Circuit design is the process of converting diverse logic networks into electronic circuitries utilizing transistors. These transistors are switching devices that are utilized in various combinations to fulfill various logic functions. The design is put to the test using computer-aided design (CAD) software, and the results are compared to the chip specifications. The designer can get a notion of the final chip’s speed, power dissipation, and performance based on these results. At this point, you can get an estimate of the chip’s size because the number of transistors determines the chip’s area. Several design variables, including transistor sizes, their counts, and circuit architecture, are optimized by experienced designers to reduce delay, power consumption, and latency, among other things. The transistors’ length and width must follow the process technology’s regulations.

Layout Design

This stage entails using CAD tools to translate the circuit created in the previous stage into a silicon description using geometrical patterns. This procedure is guided by a process rule. If these rules are broken, the chips will malfunction after fabrication. Furthermore, the designer must guarantee that the layout design appropriately reflects the circuit design and is error-free. Layout Versus Schematic (LVS) checks are available in CAD programs, and they allow you to check for mistakes as well as compare layout and circuit designs.

When an error is reported, the designer is responsible for making the appropriate adjustments. The circuit schematic is extracted from the layout drawings, which is a crucial aspect of the layout design process. All the circuit elements, wires, parasitic resistance, and capacitance are listed in the extracted circuit (a parasitic device is an unbudgeted device that inserts itself due to interaction between nearby components). This extracted file is used to simulate the silicon circuit’s electric behavior. Since this is one of the final design processes before a chip is submitted to the foundry, it’s a good idea to compare the findings to the system specification.

Fabrication

After the design has been verified, the layout is submitted to the foundry to be fabricated. Chip creation is a complicated process. Many steps of oxidation, etching, photolithography, and other processes are involved. During the fabrication process, the layout is often converted into silicon or another semiconductor material. The end result is bonded with pins for external circuit board connections Photolithographic masks are used in the manufacturing process to specify exact designs that are transferred to silicon wafers (the initial substrate used to make integrated circuits) via a number of steps depending on the process technology. In the process, the starting material, the wafer, is oxidized to generate an insulating layer. Following that is the photolithographic process, which entails depositing a photoresist on the oxidized wafer, exposing it to ultraviolet light to create patterns, and etching to remove components not covered by the photoresist. After that, the p+ or n+ source/drain region is ion-implanted, and the contacts are metalized.

The individual chip is then cut off the die in the next step. Bonding is used to link external pins. It’s vital to note that the steps in this method could be changed in any sequence to suit unique design goals. Furthermore, with very complicated devices, many of these functions are repeated multiple times. Other ways have emerged over time. One famous example is the construction of transistors using insulators (such as sapphire) as starting materials rather than semiconductor substrate (silicon on which active devices are implanted SOI technology reduces parasitic in circuits while yet allowing for high speed and low power dissipation.

Testing

Testing is the last step in the chip creation process. Oscilloscopes, Silicon Valley probe cards, pattern generators, and logic analyzers are used to test some of the chip’s characteristics to ensure that it meets the stated specifications. It’s always a good idea to run tests for diverse input patterns over a long period of time to look for potential performance deterioration, variability, or failures. Fabricated chip test results can sometimes differ from simulated findings. Depending on the application, the designer may need to re-engineer the circuit for better performance and error correction. Finally, the new design should be built and tested.

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