Table of Contents
What is end cap cells?
The end cap cell or boundary cell is placed at both the ends of each placement row to terminate the row. It has also been placed at the top and bottom row at the block level to make integration with other blocks. Some standard cell library has also corner end cap cells to place the corner of the block.
Why we use end cap cells?
To know the end of the row and at the edges, endcap cells are placed to avoid the cell’s damages at the end of the row to avoid the wrong laser wavelength for correct manufacturing. These cells ensure that gaps do not occur between the well and implant layer and to prevent from the DRC violations.
What is well tap cells?
Well tap cells (or Tap cells) are used to prevent the latch-up issue in the CMOS design. Well tap cells connect the nwell to VDD and p-substrate to VSS in order to prevent the latch-up issue.
How do you tap cells to stop latching up?
So, to prevent latch-up, special tap cells need to be inserted in the layout at the required interval to connect n-wells to VDD and p-sub to VSS based on tap rules defined inthe technology DRC file. Latch-up in CMOS is greatly caused due to high n-well and p-sub resistance.
What is implant layer in VLSI?
Ion implantation is usually performed through a mask, usually of photoresist, a layer of organic material thick enough to stop the incoming ions except where it has been patterned lithographically to expose key areas. The lithography is an essential adjunct to implantation, as with other processes used in VLSI.
What are tie cells?
Tie cells are special purpose standard cells whose output is Constant High or Constant Low. These cells are used to hold (tie) the input of other cells which are required to be connected Constant High (Vdd) or Constant Low (Vss) values.
Why N Well continuity is required?
For a clean layout you need NWELL continuity. It is imperative that you do not have well or moat spacing less than the minimum spacing(Even though you can space them apart with spacing greater than the minimum spacing, it is going to be tricky in a row of standard cells.
What is cell in VLSI?
A standard cell is a group of transistor and interconnect structures that provides a boolean logic function (e.g., AND, OR, XOR, XNOR, inverters) or a storage function (flipflop or latch).
What is latch-up problem?
Latch-Up is a condition where a low impedance path is created between a supply pin and ground. This condition is caused by a trigger (current injection or overvoltage), but once activated, the low impedance path remains even after the trigger is no longer present.
What is poly layer?
The poly layer forms the gate of the MOSFETs. Poly is a short name for polysilicon (not to be confused with the poly, or polygon, object in a layout program). Polysilicon is made up of small crystalline regions of silicon.
What is the difference between library cells and end cap cells?
End cap Cells: The library cells do not have cell connectivity as they are only connected to power and ground rails, thus to ensure that gaps do not occur between well and implant layer and to prevent the DRC violations by satisfying well tie-off requirements for core rows we use end-cap cells.
What is Decap cell and tie cell?
decap cell. Tie Cells: Tie-high and Tie-Low cells are used to connect the gate of the transistor to either power or ground. In Lower technology nodes, if the gate is connected to power/ground the transistor might be turned on/off due to power or ground bounce. These cells are part of standard-cell library.
What is end-cap cell in microcontroller?
End-cap cell are physical only cells which are added to identify end of rows in digital chips or blocks.They are also added to isolate any analog IPs and digital part of any chips.
Where to place end cap cells in a hydroponic system?
These end cap cells will be placed on both ends of the horizontal rows and vertical rows. Usually there will be different cell for horizontal and vertical end cap purpose When you insert these at the end of the placement row, these will make sure that these cells properly integrated to the design and will have a clean well.