On-Line Feedback Control of an Area-Selective Atomic Layer Deposition Spatial Reactor

Matthew Tom¹, Henrik Wang¹, Feiyang Ou¹, Gerassimos Orkoulas³, and Panagiotis D. Christofides^1,2

1. Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, CA
2. Department of Electrical and Computer Engineering, University of California, Los Angeles, CA
3. Department of Chemical Engineering, Widener University, Chester, PA

As a consequence of the miniaturization, efficiency, and applicability of high-performance semiconducting wafers, stringent design specifications limit the productivity of these devices. From nanoscale-thickness feature sizes and dependency on surface uniformities to achieve effective bottom-up fabrication, the manufacturing of semiconducting materials faces obstacles in achieving highly conformal dimensional and design criteria. To provide greater control of the semiconductor features, thin-layer deposition techniques such as atomic layer deposition (ALD) have been conducted to perform sequential cycles of monolayer deposition to maintain two-dimensional surface layering. However, conventional ALD lacks selectivity, which is needed for producing nanopatterned surfaces, and may produce nonuniform surfaces. Thus, area-selective atomic layer deposition (ASALD) has been integrated into semiconductor fabrication methods as a bottom-up fabrication technique that produces highly conformal, nanopatterned, and uniform surfaces [1]. Despite ASALD processes being studied experimentally, there is limited study of the ASALD process in larger scales due to the complexity of process and operation optimization as well as process control. Prior work [2] established an in silico multiscale computational fluid dynamics (CFD) simulation framework that would characterize the various atomistic, mesoscopic, and macroscopic phases through a combination of ab initio molecular dynamics, kinetic Monte Carlo, and CFD simulation, respectively. However, prior research limited the discussion of pursuing on-line monitoring of the process by assuming a constant operating temperature environment, which is necessary to prevent the pyrolysis of byproducts generated from reagents such as bis(diethylamino)silane (BDEAS) at higher operating temperatures [3]. Additionally, ozone decomposition can produce oxygen gas, which is a combustion agent that could yield a runaway reaction that would lead to reactor instability [4]. Thus, an effective control system must be implemented to the proposed ASALD reactor to ensure that the operation stability is maintained under the presence of temperature disturbances that will impede the operation and control of the process [5].

This work will examine the development of a feedback control system on the operating temperature to a prior rotary spatial reactor for an ASALD process. Temperature adjustments will be performed under the presence of various temperature disturbances to the feed, boundary walls, and reactor operating conditions, which are quantified by step, impulse, or ramp disturbances. Additionally, a model predictive control system is integrated into the prior CFD simulation model through user-defined functions to regulate the surface temperature using several temperature elements. To improve the controller performance, the strategy of temperature metrology, which is spatially applied on the wafer, is studied.

References:

1. Mackus, A. J. M., Merkx, M. J. M., & Kessels, W. M. M., 2019. “From the bottom-up: toward area-selective atomic layer deposition with high selectivity,” Chemistry of Materials, 31, 2-12.
2. Yun, S., Wang, H., Tom, M., Ou, F., Orkoulas, G., & Christofides, P. D., 2023. "Multiscale CFD modeling of spatial area-selective thermal atomic layer deposition: application to reactor design and operating condition calculation," Coatings, 13, 558.
3. Stevenson, J. M. & Shi, Y., 2021. “Theoretical study of decomposition kinetics and thermochemistry of bis(dimethylamino)silane—formation of methyleneimine and silanimine species,” Journal of Physical Chemistry A, 125, 8175-8186.
4. Benson, S. W., Axworthy, A. E., 1957. “Mechanism of the gas phase, thermal decomposition of ozone,” Journal of Chemical Physics, 26, 1718-1726.
5. He, W., Chu, B., Gu, R., Zhang, H., Shan, B., & Chen, R., 2013. “The application of generalized predictive control in the radiant heating atomic layer deposition reactor,” 2013 IEEE International Symposium on Assembly and Manufacturing (ISAM), Xi'an, 37-40.