Comment
Author: Admin | 2025-04-28
Supply network. These will affect reliability, speed and signal integrity. The addition of on-chip decoupling MIMCAP compensate voltage fluctuations by supplying charges to the power network. However, the capacitance must be large enough to meet the requirement. MIMCAP Structure Figure2. MIMCAP Structure In 16nm project, the MIMCAP was placed between Metal 12 and Metal 11. A Metal-Insulator-Metal Capacitor (MIMCAP) uses a cut layer (V11) that connects a metal layer M12 to metal layer M11. The cut layer (V11) connects top layer metal layer M12 to intermediate layers CBM and CTM. The intermediate layers (CBM and CTM) are defined in the technology file with the MIMCAP function. Layer Function Mask M12 Metal 42 V11 Cut 61 CTM MIMCAP 77 CBM MIMCAP 88 M11 metal 41 Table 2: Layer Function table for MIMCAP from Foundry. Figure 3: Base Cell + Metal11/Via11 Power Grid Above figure shows 4X4 MIMCAP of size 46x55 um^2.The cell cap is 42pF and Cap Density = 42700fF / (46.08*55.296 um^2) = 16.8 fF/um^2. It is a cover cell. It has via11 obstruction in MIM region and M11 obstruction under MIM vias. It has no CTM/CBM shapes. Coupling to CTM/CBM seen only in extraction. Where to Add? MIMCAP cells are added to the blocks after power grid insertion. Decap cells are still required. MIMCAP doesn’t replace decaps, it rather adds to it. It is recommended to add these to places where there is little or no metal11 routing, since coupling to metal11 won’t be seen until extraction. It is recommended adding over high current density areas, such as TCAMs, high density or frequency logic areas, etc. There are placement rules regarding MIMCAP and die edge. Recommend >400u away from die edge. Conclusion: In our 16nm networking chip of 22*15 mm size with mentioned usage of MBIT flops and MIMCAPs,
Add Comment