Skip to main content

🅦🅗🅨 the resistivity of the top metal layers will be low compared to the lower metal layers eve though you use the same metal for all the layers?

Image
By
Why the resistivity of the top metal layers will be low compared to the lower metal layers eve though you use the same metal for all the layers?

Theoretically, one would want to have all metal layers with low resistance. Practically, there are limitations - cost and technology - that lead to finite metal resistance .All metal layers can be made of copper, and copper has much lower resistance than aluminum (~1.7e-6 Ohm*cm vs ~2.7e-6 Ohm*cm). However copper technology is more expensive than aluminum technology, so there is a cost-performance trade-off. 

From technology viewpoint, you can make a metal layer very thick (to make sheet rho value lower), but then you can not make metal line very narrow (lateral coupling capacitance increases and results the cross talk) .So if you want to achieve very fine metal pitch (to provide high integration density - i.e. number of devices per unit area), the metal thickness can not be made very large. The solution is to use thinner (and thus more resistive) metal layers for low layers (i.e. M1, M2 ...) and for local routing, and thicker (less resistive) layers with larger width and spacing for long-range routing on the higher levels.

Comments

Post a Comment

Popular posts from this blog

Sanity checks before floorplan in Physical Design

By
Sanity checks before floorplan in Physical design Sanity checks are an important step for physical design engineers to make sure that the inputs received for physical design are correct and consistent. Any issues in the input may cause problems in the later stages. So it is important to perform the sanity checks in the initial stage that is when the design is loaded in PnR tool and before the start of the floorplan. Here is a list of checks which must be performed before floorplan of design. Figure-1: Sanity checks before floorplan Library Check: In library check, basically, we validate the libraries before starting the physical design by checking the consistency between the physical and logical library.  It also checks the quality of both libraries and reports the error if any. The cells used in the design must be present in the logical as well as in the physical library. Innovus commands: check_design -physicalLibrary :  This command will check the physical library and repor...
Post a Comment
Read more

Why we are not checking the hold before CTS?

By
  Why we are not checking the hold before CTS? Ans: Before CTS, clock is ideal that means exact skew is not there. All the clocks reaching the flops at the same  Time. So, we dont have skew and transition numbers of the clock path, but this information is sufficient to  perform setup analysis since setup violation depends on the data path delay. Clock is propagted only after CTS  (actual clock tree is built, clock buffers are added & clock tree hierarchy, clock skew, insertion delay comes into  picture) and that's why hold violations are fixed only after CTS.
Post a Comment
Read more

Scope and opportunities in VLSI @ 2021

By
Scope and opportunities in electronics and VLSI in 2021 Scope and opportunities in electronics and VLSI in 2021 It is very important to know the  scope of electronics and semiconductor engineering  for engineering students and about the industry growth. If you are not sure about the  How to make career in VLSI Semiconductor industry , then stick to the end of this blog to know everything about semiconductor industry.    Through this blog i will touch upon all the question that come in every fresher's mind during his electronics engineering time  . What is electronics engineering ? What is Future and Scope of Electronics Engineering ? Do we have jobs in core electronics field ? What types company exist in electronics industry ? What types of skill set required to enter in semiconductor VLSI company ?  Nowadays the electronics industry is growing very fast, due to which the electronics engineer scope has increased greatly in India as well. In the la...
Post a Comment
Read more