Test: Design Rules And Layout - Electrical Engineering (EE) MCQ

Circuit design concepts can be represented using stick diagrams and symbolic diagrams. Stick diagrams represents different layers with color codes. Symbolic diagram represents the structure with symbols with color codes.

Circuit designers in general prefer tighter, smaller layouts for improved performance and decreased silicon area.

 Process engineers wants design rules which are controllable and reproducible process.

Yes, the maturity level of the process line affects design rules.

Design rules specify line widths, separations and extensions in terms of lambda.

 The width of n-diffusion and p-diffusion should be 2λ according to design rules.

The spacing between two diffusion layers should be 3λ according to design rules and standards.

The width of the metal 1 layer should be 3λ and metal 2 should be 4λ.

Implant for a n-mos depletion mode transistor should extend minimum of 2λ from the channel in all the directions.

Buried contacts are much better than butted contacts. In butted contacts the two layers are joined together or binded together using adhesive type of material where as in buried contact one layer is interconcted or fitted into another.

Micron rules occupies or consumes lesser area. 50% of the area usage can be reduced by using micron rules over lambda rules.

 Lambda rules gives scalable design rules and micron rules gives absolute dimensions.

Lambda design rules prevents shorting, opens, contact from slipping out of area to be contacted.

Diffusion and polysilicon layer are joined together using butting contact. In butting contact the two layers are joined or binded together.

Butting contact is complex process whereas buried contact is simple process because butting contact should be done more carefully to serve well and be strong.

Buried contact occupies smaller area than butting contact as in buried contacts one layer will be completely within or almost within the another layer.

Isolation layer between two metal layers should be thicker. Metal to metal separation is large and is brought about mainly by difficulties in defining metal edges accurately.

The oxide layer below the first metal layer is depostied using chemical vapour deposition method. This is a chemical process used to produce high quality high performance solid materials.

 Metal layers are used for power and signal lines as metals has good thermal and electrical conductivity.

The minimum feature size for thick oxide is 3λ and minimum separation between thinox regions is also 3λ.

 Hatching is compatible with monochrome encoding and also may be added to color mask coding. It is designed using closely spaced lines or sticks.

The minimum width of n-well is 3 micro meter because n-well should be with little thickness and in it p-type devices are formed.

The minimum spacing between two n-well is 8.5 micro meter according to the lambda based design rules.

One of the problem in the manufacture using design rule is that variation in threshold voltage occurs. And this is caused by oxide thickness, ion implantation and poly variations.

Some of the advantages of generalised design rules are those are durable, scalable, portable, increases designer efficiency and automatic translation to final layout can be done.