The document discusses layout design rules that specify minimum feature sizes and separations between layers for a chip manufacturing process. Design rules are described using either micron or lambda units. Lambda rules specify widths of diffusion and polysilicon layers as well as minimum separations between layers. There are also design rules for metal layers and forming transistors. The document describes three approaches for contact cuts between polysilicon and diffusion layers: using polysilicon to metal to diffusion, buried contacts, and butting contacts using metal.

1. Layout DesignRules
The physicalmask layout of any circuit to be manufactured using a particular
process mustconformto a set of geometric constraints or rules, which are
generally called layoutdesign rules.
These rules usually specify the minimum allowable line widths for physical
objects on-chip such as metal and polysilicon interconnects or diffusion areas,
minimum feature dimensions, and minimum allowable separations between
two such features.
The design rules are usually described in two ways :
• Micronrules, in which the layout constraints such as minimum feature sizes
and minimum allowable feature separations, arestated in terms of absolute
dimensions in micrometers.
• Lambda rules, in which the layoutconstraints such as minimum feature sizes
and minimum allowable feature separations, arestated in terms of absolute
dimensions in ( ) .
Lambda baseddesignrules :
The following diagramshow the width of diffusions(2 ) and width of the
polysilicon (2 ).
And it also representthe minimum separation between layers and they are
1.Separation between P-diffusion and P-diffusion is 3
2.Separation between N-diffusion and N-diffusion is 3
3.Separation between P-diffusion and Polysilicon is 1
4. Separation between N-diffusion and Polysilicon is 1
5. Separation between Polysilicon and Polysilicon is 2

2. The followingdiagramshowthe widthof metals1(3 ) andmetal2(4 ).
1. Separationbetween Metal1andMetal1 is 3
2. Separationbetween Metal2andMetal2 is 4
Transistor design rules:-
By overlapping the polysilicon with N-diffusion form the NMOS
And overlapping the polysilicon with P-diffusion form the PMOS
After forming the enhancement NMOS if it was implant then it converts to depletion NMOS

3. Contact Cuts:-
• Whenmakingcontacts betweenpolysiliconanddiffusioncircuitsitshouldbe recognized
that there are three possible approaches
1.Polysilicontometal thenmetal todiffusion
2.Buriedcontactpolysilicon todiffusion
3.Buttingcontact (Polysilicontodiffusionusingmetal)
1.Polysiliconto metal then metal to diffusion :-
Whencontact cut is createdbetweenmetaltopolysiliconandmetal to diffusionis2 x 2
and itwas superimposedwith4 x 4 .
Andthe minimumseparationbetweencontactcutsis2
2.Buried contact polysilicontodiffusion:-
i.The contact cut in these case indicating where the thin oxide is etched to
reveal the surfaceof the silicon wafer beforepolysilicon is deposited.
ii.Then diffusion is carried out into the exposed surface. when diffusion takes
place impurities will diffuseinto polysilicon as well as diffused area within the
contact area.
iii.It tell that connection between polysilicon and diffusion .

4. 3.Butting contact (Polysilicontodiffusionusingmetal):-
Buttingcontact iscomplex .A 2 x 2 contact cut is made downto eachlayersto be joined.Layers
are buttedtogethersothat two contact cuts become contiguous.
The polysiliconanddiffusionlayersare buttedtogether.Andthe contactbetweentwobuttinglayers
isthenmade by a metal overlays