The CAP_TOP_METAL layer is used exclusively for the construction of metal-to-metal capacitors. The bottom plate of the capacitor is one of the regular metal layers, as specified below. CAP_TOP_METAL is the upper plate of the capacitor; it is sandwiched physically between the bottom plate metal and the next metal layer above, with a thin dielectric between the bottom plate and the upper (CAP_TOP_METAL) plate.
The CAP_TOP_METAL can only be contacted from the metal above; the bottom plate metal can be contacted from below or above (subject, in either case, to rule 28.5), and/or by bottom metal extending outside of the capacitor region (rule 28.7). Use of all (legal) upward vias within that region should be maximized. CAP_TOP_METAL must always be contained entirely within the bottom plate metal.
Process | Bottom Plate | Top Plate | Top Plate Contact |
TSMC_025 | METAL4 | CAP_TOP_METAL | VIA4 and METAL5 |
TSMC_018 | METAL5 | CAP_TOP_METAL | VIA5 and METAL6 |
Rule | Description | Lambda | ||
SCMOS | SUBM | DEEP | ||
28.1 | Minimum Width, Capacitor | n/a | 40 | 45 |
28.2 | Minimum Spacing (2 capacitors sharing a single bottom plate) | n/a | 12 | 14 |
28.3 | Minimum bottom metal overlap (including dummy shapes) | n/a | 4 | 5 |
28.4 | Minimum overlap of via | n/a | 3 | 3 |
28.5 | Minimum spacing to bottom metal via | n/a | 4 | 5 |
28.6 | Minimum bottom metal overlap of its via | n/a | 2 | 2 |
28.7 | Rule applicability region extends beyond bottom plate | n/a | 25 | 25 |
28.8 | Minimum width, dummy shapes (having no vias) | n/a | 4 | 5 |
28.9 | Minimum bottom plate to other bottom plate metal | n/a | 8 | 9 |
28.10 | Minimum via separation, on CAP_TOP_METAL | n/a | 20 | 23 |
28.11 | Minimum (upward) via separation on bottom metal | n/a | 40 | 45 |
28.12 | Maximum CAP_TOP_METAL width and length | n/a | 30 um | |
28.13 | Maximum bottom metal plate width and length | n/a | 35 um | |
28.14 | No vias from bottom plate downward, directly under top plate CAP_TOP_METAL; dummy metal shapes under capacitor region, discouraged. | |||
28.15 | No active or passive circuitry under capacitor region |