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The recent demonstration of W mm−1output power at 94 GHz in AlN/GaN/AlN high‐electron‐mobility transistors (HEMTs) has established AlN as a promising platform for millimeter‐wave electronics. The current state‐of‐art AlN HEMTs using ex situ‐deposited silicon nitride (SiN) passivation layers suffer from soft gain compression due to trapping of carriers by surface states. Reducing surface state dispersion in these devices is thus desired to access higher output powers. Herein, a potential solution using a novel in situ crystalline AlN passivation layer is provided. A thick, 30+ nm‐top AlN passivation layer moves the as‐grown surface away from the 2D electron gas (2DEG) channel and reduces its effect on the device. Through a series of metal‐polar AlN/GaN/AlN heterostructure growths, it is found that pseudomorphically strained 15 nm thin GaN channels are crucial to be able to grow thick AlN barriers without cracking. The fabricated recessed‐gate HEMTs on an optimized heterostructure with 50 nm AlN barrier layer and 15 nm GaN channel layer show reduction in dispersion down to compared with in current state‐of‐art ex situ SiN‐passivated HEMTs. These results demonstrate the efficacy of this unique in situ crystalline AlN passivation technique and should unlock higher mm‐wave powers in next‐generation AlN HEMTs.
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Mitigation of Electromigration in Metal Interconnects via Hexagonal Boron Nitride as an Ångström‐Thin Passivation Layer
Abstract Electromigration in metal interconnects remains a significant challenge in the continued scaling of integrated circuits towards ever‐smaller single‐nanometer nodes. Conventional damascene architectures of barrier/liner layers and conducting metal cause inevitable compromises between device performance and feature dimensions. In contrast to contemporary barrier/liner materials (e.g., Co, Ta, and Ru), an ultrathin passivation layer that can effectively mitigate electromigration is needed. At the ultimate atomically‐thin limit, 2D materials are promising candidates given their exceptional mechanical properties and impermeability. Here, a facile and effective approach is presented to mitigating electromigration in copper (Cu) interconnects via passivation with insulating monolayer 2D hexagonal boron nitride (hBN). The hBN‐passivated Cu interconnects, compared to otherwise identical but bare Cu interconnects, exhibit on average a >20% higher breakdown current density and a >2600% longer lifetime (at a high current density of 5.4 × 107A cm−2). Post‐mortem metrology elucidates uniform conformal contact between the hBN‐passivated Cu interface and common failure features due to electromigration.
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- PAR ID:
- 10450977
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Electronic Materials
- Volume:
- 7
- Issue:
- 6
- ISSN:
- 2199-160X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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