Molybdenum: The New Frontier in Semiconductor Metallization according to Lam Research

The semiconductor industry is facing a significant shift as Molybdenum (Mo or Moly as the Americans say) is tipped to replace tungsten in chip manufacturing due to its superior atomic-scale properties. Kaihan Ashtiani, Corporate Vice President and General Manager at Lam Research, highlights the critical attributes of moly that make it the ideal choice for advanced devices. The company is at the forefront, aiding chipmakers in the transition with its ALTUS® product family, drawing from its pioneering work in Tungsten ALD and expertise in 3D NAND technology.

The semiconductor sector is on the cusp of a pivotal transition with molybdenum poised to supersede tungsten for interconnect metallization in response to the stringent scaling demands of modern chipmaking. Molybdenum's edge lies in its low resistivity and ease of integration into existing semiconductor processes, including atomic layer deposition (ALD) and chemical-mechanical planarization (CMP). These properties, combined with its minimal diffusivity into dielectric materials—thus negating the need for a barrier liner—make moly the preferred candidate for next-generation devices. Kaihan Ashtiani of Lam Research articulates the advantages of moly over other metals like cobalt and copper and underscores Lam's commitment to facilitating this industry shift. Leveraging decades of expertise and innovation in tungsten ALD and the transition from 2D to 3D NAND, Lam's ALTUS® product line is instrumental in enabling widespread adoption of molybdenum. This shift is not just theoretical; major chipmakers are actively exploring moly integration, marking a significant evolution in semiconductor fabrication.

The ALTUS® system by Lam Research is a suite of metal deposition tools used in semiconductor manufacturing, particularly for the deposition of tungsten and potentially other metals like molybdenum. These systems are designed to deposit metals by CVD or later named PNL (Pulsed Nanolayer deposition) and today marked as Atomic Layer Deposition (ALD- yeah!), which allows for extremely fine control of film thickness and composition at the atomic level, crucial for creating the tiny, densely packed structures found on modern integrated circuits.

For tungsten, the ALTUS® system has been a workhorse in the industry for the deposition of tungsten films, especially in the fabrication of the contact and via layers of integrated circuits. The ALD process ensures excellent step coverage, conformality, and uniformity even in very high aspect ratio structures. This is particularly important for Logic, DRAM, and 3D NAND applications, where the precise control of the tungsten film's electrical and physical properties is critical for device performance.

ALTUS applications

Logic devices, metallization needs to meet the requirements of increasingly smaller geometries and higher performance. The precision of ALD with tungsten and potentially molybdenum is essential for creating the necessary electrical connections without compromising the device's integrity.

  

Dynamic Random-Access Memory (DRAM) requires highly reliable and conductive connections as it is constantly refreshed to maintain data. The metallization process for DRAM needs to ensure that the metal films provide low resistivity and high reliability for the memory to function correctly.

  

In 3D NAND flash memory, multiple layers of memory cells are stacked vertically. This requires extremely uniform metal layers across all the stacked levels. The ability of the ALTUS® system to deposit tungsten and potentially molybdenum with high uniformity and excellent conformal coverage is vital for the success of 3D NAND devices.

Sources:

ALTUS Product Family - Lam Research