13.3 Design rules for Dummy Metal addition

For good metal etch process margin, a minimum metal density is recommended for Metaln and MetalTop. Device (circuit) layouts that does not meet minimum pattern density rule (stated in the metal design rules) shall be added in the dummy metal patterns. Dummy metals are added to improve the overall metal density so as to reduce the potential dishing issue due to CMP also.

Generation method:

  1. Check the metal density in an area of 200um by 200um at a step of 100um.

  2. Add dummy metal if total die metal density is less than 30%

  3. Dummy metal size: 2.0um x 2.0 um; space is 1.2um

  4. Please follow the following table when generating the Dummy metals:

Dummy Metal rules

RULE NO.

DESCRIPTION

LAYOUT GUIDELINE

Layer

DMF – Dummy Metal Fill

Use PMNDMY mark layer to exclude dummy metal generation in

certain critical analog/RF areas.

DM.1

Min/Max Dummy metal line width/length

2.0 um

DM.2a*

Min Dummy metal line space (for Layout)

1.2 um

DM.2b

Min Dummy metal line space (for DRC)

0.98um

DM.2c

Min Dummy metal line space for thick top metal (3um Top metal)

2.0um

DM.3

Minimum space between dummy metal and circuit Metal line

2.0um

DM.4

Dummy Metal space to Subsequent Metal layer (E.g. Dummy M1

space to M2)

1um

DM.5

Dummy Metal space to Previous Metal layer (E.g. Dummy M2

space to M1; Dummy M1 space to Poly2)

1um

DM.6

No overlap of Dummy Metal with the Subsequent Metal layers

DM.7

No overlap of Dummy Metal with the Previous layers

DM.8

There should not be any dummy metal pattern fill in the following areas

  1. MIM CAP area (recognized by Fuse Top)

  2. Poly fuse area (recognized by POLYFUSE)

  3. Metal fuse area (recognized by FUSEWINDOW_D)

  4. Dummy metal exclusion area (recognized by PMNDMY)

  5. MTP mark area (recognized by MTPMK)

  6. OTP mark area ( recognized by OTP_MK)

Space from these Structures

6um

DM.9*

Do not use exact replicates of dummy metal fill patterns for

consecutive metal layers to avoid dielectric and metal stress

problems? E.g. the Metal4 dummy metal fill patterns should not be

an exact copy of the Metal3 dummy fill pattern. (Offsets value:)

0.5um

DM.10*

Offset between the Dummy metal of the same layers

0.5um

Dummy Poly2