SBIR-STTR Award

Atomically precise placement of dopants in 2D planes inside semiconductor crystals has shown enormous potential for creating valuable structures such as analog quantum simulations and devices such as qubits for quantum computers ultra-high performance analog transistors, and potentially quantum metamaterials with designer quantum properties. These applications will have an enormous impact on energy efficiency as well as other important attributes important to our nation’sinterest. This technology has a number of unique and powerful advantages already realized and more capabilities are being developed: Ability to place dopant atoms (primarily P donors) in a single buried (100) plane of a Si or Ge crystal. Emerging capabilities to place acceptor (B and Al) dopants and heavier donor (As) dopants. Doping levels can be extremely high in a single (100) plane. As much as ¼ monolayer of P atoms in a single Si (100) plane renders metallic conducting material that is also direct bandgap. Even higher doping levels have been obtained and ongoing improvements in doping levels may produce 2D superconducting semiconductor material. These delta doped layers have 5-6 orders of magnitude less 1/f noise. The ability to pattern with atomic precision the 2D regions that dopants are placed in. Near deterministic control of doping in a given region. By repeating these 2D patterning and dopant placement after epitaxial growth the atomically precise dopant placement can be extended to 3D designs. A current limitation in these potentially revolutionary devices and structures is the ability to control exactly the number of dopant atoms that end up in specific nanoscale elements. For instance in spin donor qubits the number of dopant atoms that make up a single qubit is extremely important and currently the methods of placing the dopant atoms is stochastic in nature. There are attempts at developing methods that are deterministic, but there is no dopant counting metrology technology to guide this development and verify the numbers of dopant atoms in production. Building on our Atomically Precise Patterning tool which is integral to creating these 2D structures and devices, we will integrate into this tool the ability to count individual dopant atoms beneath the surface and verify that specific nanoscale areas contain the desired number of dopant atoms. This will be accomplished by using a specific modality of scanning tunneling microscope imaging. We intend to develop a method that operates at room temperature rather than cryogenic temperatures which will make the process more affordable and will reach a larger market.

The overall objective of this program is to improve the metrology of buried dopant structures for ultraprecise devices created using Scanning Tunnelling Microscope (STM) based lithography. During fabrication, it is necessary to determine the location of existing structures so as to align new dopant structures to them precisely. This metrology therefore needs to be done in-situ during fabrication with the same probe as used for lithography Second, for quantum devices, it is proving more important that there be the desired number of dopants in a patch, rather than that their position is atomically precise. In-situ metrology allows the possibility of error correction. This is a hallmark of Atomic Precision Advanced Manufacturing. The dopant deposition and incorporation is performed in a different chamber than the lithography. Therefore, after incorporation, we need methods to reliably and efficiently relocate the general area of the nm-scale dopant structures on a mm-size sample, determine the exact location of the dopants, and to provide as far as possible quantitative information about the dopant number and location. Thus far, in the initial Phase I program, we have used a closed-loop coarse motion system and patterned substrates to return efficiently to the same position on a sample. We have developed novel high-frequency STM-based spectroscopic methods to measure dI/dV and I- V spectra at high speed during scanning, and have successfully used these methods to create bipolar dopant structures by locating B dopant regions, and then aligning P dopant patterns to them. In Phase II, we will continue to develop these novel spectroscopic imaging methods. We will pursue two tracks: metrology of dopant patch location to support Atomically Precise device fabrication for the DOE objective of UltraPrecise Manufacturing, including our parallel STTR on fabrication of bipolar devices, DE-SC0020817; and single-pixel-scale experiments to determine the sensitivity of the novel spectroscopic methods to the number of dopants in small patches to support the fabrication of quantum devices. These metrology capabilities will be incorporated into our ultraprecise lithography tool, ZyVector, enhancing its commercial value, and improve the yield and throughput of manufactured ultraprecise dopant-based devices.