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Via Level Airgap Interconnect

IP.com Disclosure Number: IPCOM000235775D
Publication Date: 2014-Mar-25
Document File: 5 page(s) / 59K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is an approach for a via level airgap interconnect. The method is to replace the dielectrics at via levels with air (k1), in order to greatly reduce interlevel capacitance. The approach also uses refractory metal in the via to improve reliability.

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Via Level Airgap Interconnect

With aggressive technology scaling, it is necessary to achieve lower RC without sacrificing good reliability. Known solutions include line level airgaps; however, this has difficulty passing reliability due to damage to metal lines.

Via height is almost equal to line height. Via level metal density is much lower than line level metal density.

The solution is a method to replace the dielectrics at via levels with air (k1), in order to greatly reduce interlevel capacitance. The solution also uses refractory metal in the via to improve reliability.

Figure 1: Example: 22nm Mx PA

The solution comprises:

Partial or full airgap at via levels


Via is made of refractory metal
Trench is made of low resistive metal
Permeable HM under trench dielectrics and Impermeable cap above trench dielectrics

Figure 2: Proposed Structure I

Figure 3: Proposed Structure II

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Figure 4: Proposed Structure III

To implement the solution in a preferred embodiment:

1. Deposit sacrificial dieletric and permeable HM, then pattern to define via (Figure
5)

2. Fill in refractory metal, then use Chemical Mechanical Planarization (CMP) to planarize (Figure 6)

3. Slowly raise temperature to 3500C-4500C to remove sacrificial dielectric materials (Figures 7 and 8)


4. Deposit next layer dielectric, pattern to form trenches (Figure 9)


5. Deposit barrier/seed, Metal filling then SiCxNy cap (Figure 10)

Figure 5: Step 1: Deposit sacrificial dieletric and permeable HM, then pattern to define via

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100 is the sacrificial dielectric material that can decompose 3500C - 4000C. (e.g., polystyrenes, polymethyl methacrylates, polynorbornenes, and polypropyl...