Materials innovation has always been vital to the semiconductor industry. In the past, it was high-κ gate dielectrics. Today, Cobalt is seen as a replacement for Tungsten in middle-of-line (MOL) contacts.
What materials innovation will the future bring?
A likely answer is Graphene, the wonder material discovered in 2004.
Graphene is one atomic layer of carbon, the thinnest and strongest material that has ever existed. It is 200 times stronger than steel and the lightest material known to man (1 square meter weighing around 0.77 mg). It is an excellent electrical and thermal conductor at room temperature with an electron mobility of ~ 200,000
cm2.V-1.s-1. At one atomic layer, graphene is flexible and transparent. Other notable properties of Graphene are its uniform absorption of light across the visible and near infrared spectrum and its applicability towards spintronics-based devices.
Graphene and Moore’s Law
Moore’s Law scaling can be broken down into 4 key areas:
- Advanced Packaging (2.5D and 3D IC)
- Interconnect Material
Solutions for upcoming nodes are starting to emerge in the first two areas (EUV and Nanowire- or Nanosheet-based FET respectively). Graphene play an important role in the latter two areas. For advanced packaging, Graphene can be used as a heat spreader (to lower overall thermal resistance), or as an EM shield (to lower crosstalk) as part of a 3D IC package.
Active Graphene device layers can potentially be stacked on top of each other using a low-temperature transfer process (< 400°C) to allow for a dense heterogeneous “memory near compute” configuration. This is an area DARPA is actively researching as part of its new $1.5 billion Electronics Resurgence Initiative.
Regarding interconnects, Copper interconnects are running out of steam and becoming a major IC bottleneck (projected 40% total delay for 7 nm node). Graphene’s high electron mobility and thermal conductivity make it an attractive interconnect material for MOL and back-end-of-line (BEOL), especially at line widths < 30 nm.
Graphene Device Applications
Graphene-based semiconductor applications are already starting to hit the market. A fully integrated optical transceiver (with a Graphene modulator and photodetector) operating at 25 Gb/s/channel was on display at the recent Mobile World Congress in Barcelona. San Diego-based Nanomedical Diagnostics is selling a medical device that uses a Graphene biosensor. Europe-based Emberion is building Graphene optoelectronic sensors that might find a home in LIDAR applications, where there is currently a focus on improving sensing in low-light conditions.
What will the overall Graphene roadmap in the semiconductor industry look like? The history of ion implantation serves as a good example of how a fundamental scientific discovery moves from the lab to the foundry floor.
The dominant view in the semiconductor industry at the time was that ion implantation would not work in practice (vs. thermal diffusion) and that, if it did, it would only marginally improve the manufacturing yields of existing products. There was nothing obvious about the transfer of ion bombardment techniques from nuclear physics research to semiconductor production.
Varian (led by British physicist Peter Rose) built a new, advanced ion implant tool that Mostek (DRAM manufacturer based in Texas) was able to use to create MOS ICs with clear competitive advantages. The successful collaboration between Varian and Mostek was the turning point in the development of ion implantation as a major semiconductor manufacturing process. Over the next few years, semiconductor firms used ion implantation in a growing number of process steps and, by the late 1970s, it became one of the main processes used in semiconductor manufacturing.
Likewise, the Graphene world needs to work closely with the semiconductor industry to develop the tools and techniques required to solve fundamental issues around Graphene growth (good uniformity over large area, low defect density) and Graphene transfer (high throughput, CMOS compatible). It is only then will we fully realize a future that includes 2D materials.
The first step in this process is cross-industry education and initiating the dialogue between semiconductor industry and graphene companies. The National Graphene Association will be hosting the largest gathering of graphene companies and commercial stakeholders at the Global Graphene Expo & Conference, October 15-17, 2018, in Austin, Texas.
Learn more about graphene at the upcoming Global Graphene Expo & Conference with dedicated panels of experts and investors, and roundtable discussions on how Graphene will impact the semiconductor industry. The event promo code is SEMINGA.
Anand Chamarthy is the CEO and Co-Founder of Lab 91, an Austin-based startup that is working towards Graphene/CMOS integration at the foundry level. Anand can be reached at [email protected].