Beol Compatible High-Capacitance Mimcap Structure Using ZrO 2 with Enhanced Dielectric Constant

We demonstrate a MIM capacitor structure using ZrO 2 for the dielectric layer which exhibits a 25% capacitance increase (from ~43fF/mm 2 to >55fF/mm 2 for a ~55 Å film) with minimal leakage current increase compared to Hf based dielectrics, extending the usefulness of MIM on-chip decoupling capacitors. The MIM structure, suitable for BEOL processing is TiN/ZrO 2 /TiN combined with an anneal which is shown to improve the capacitance vs. leakage performance compared to doped and undoped HfO 2 based control structures. GI-XRD measurements demonstrate that the capacitance increase corresponds with a phase transformation of the ZrO 2 from amorphous to cubic phase, which is shown to have a dielectric constant ( k ) up to 35. Reliability models based on hard-breakdown (HBD) show that this structure exceeds the end-of-life targets. Servers and high-performance chips have historically relied on on-chip decoupling capacitors (decap) to reduce power supply noise in order to achieve 3 – 5.4 GHz operating frequency. Although packaging decap can be very effective at mitigating low and mid-frequency noise, on-chip decap, such as MIMCAP, is critical for mitigating mid and high-frequency noise. As Fig. 1 shows, an increase in on-chip decap can result in a significant performance benefit, due to their fast response time slowing the fastest droops, giving time for slower response elements to contribute. One method of achieving this increased decap is to increase the k of the material being used as the insulator in the MIMCAP. Following high- k gate dielectric technology, HfO 2 and other Hf based dielectric stacks have been used for this layer successfully [1]. But there is a significant difference in the thermal budget that the dielectric is exposed to following the deposition between gate dielectric and MIMCAP applications. The gate dielectric, deposited prior to any metallization, will typically be exposed to a relatively high thermal budget compared to the insulator layer of a decoupling MIMCAP, which is usually placed between wiring levels in the back end of the line (BEOL) [2]. Since the thermal budget after deposition will affect the crystal structure of a material, and different crystal phases of the same material can have dramatically different dielectric constants [3], the actual dielectric constant of a particular high- k material may vary significantly depending on whether it is used as the gate dielectric or as the MIM insulator. In this work, we explore the use