AVS 65th International Symposium & Exhibition
    Thin Films Division Tuesday Sessions
       Session TF+AM+EM+PS-TuM

Paper TF+AM+EM+PS-TuM4
Topographical Selectivity with BN Electron-Enhanced ALD

Tuesday, October 23, 2018, 9:00 am, Room 104B

Session: Atomic Layer Processing: Area Selective Deposition
Presenter: Jaclyn Sprenger, University of Colorado at Boulder
Authors: J.K. Sprenger, University of Colorado at Boulder
A.S. Cavanagh, University of Colorado at Boulder
H. Sun, University of Colorado at Boulder
A. Roshko, National Institute of Standards and Technology
P. Blanchard, National Institute of Standards and Technology
S.M. George, University of Colorado at Boulder
Correspondent: Click to Email

Electron-enhanced atomic layer deposition (EE-ALD) is a new growth technique using sequential self-limiting exposures of electrons and precursor. The electrons produce dangling bonds at the surface through the process of electron stimulated desorption (ESD). The dangling bonds then facilitate the adsorption of precursor resulting in film growth. Because the electron flux is directional, EE-ALD can be used for selective area deposition. For portions of the sample that are masked from the e--beam, no dangling bonds are produced and no film growth occurs. Additionally, any portion of the surface that is parallel to the e--beam, e.g. the walls of a trench, may be considered topographically masked because the e--beam is not incident on the surface.

The topographically selective area deposition by EE-ALD was investigated by depositing boron nitride (BN) EE-ALD films on a trench structure. EE-ALD of BN has been demonstrated using sequential exposures of borazine (B3N3H6) and electrons (50-450 eV) at room temperature [1]. GaN [2] and Si [3] have also been deposited earlier using EE-ALD. The topographical selectivity was investigated by growing an EE-ALD BN film on a trench structure. On the vertical walls of a trench structure, aligned parallel to the e--beam, there should be no electron flux and no film. In contrast, the top and bottom of the trench will receive the full flux of the e--beam. To test these ideas, high resolution TEM images were recorded after 1000 cycles of BN EE-ALD on a trench structure.

BN films were observed on the top and bottom of the trench. For the trenches used in this study, the side walls were not vertical. Some BN film deposition did occur on these sidewalls, but at a lower growth rate than the horizontal surfaces at the top and bottom of the trench. The electron flux on the side walls was reduced by a factor of cos θ where θ is the angle between the surface normal of trench wall and the e--beam. Incorporating the reduced electron flux into the model for EE-ALD film growth showed excellent agreement with film thicknesses observed on the trench walls. The topographic selectivity of EE-ALD, demonstrated with BN, coupled with a metal chemistry, would offer a promising solution to challenges such as the bottom-up-fill of conductors in trenches or vias.

[1] J. K. Sprenger, H. Sun, A. S. Cavanagh, A. Roshko, P. T. Blanchard and S. M. George, J. Phys. Chem. C. DOI: 10.1021/acs.jpcc.8b00796 (2018).

[2] J.K. Sprenger, A.S. Cavanagh, H. Sun, K.J. Wahl, A. Roshko and S.M. George, Chem. Mater. 28, 5282 (2016).

[3] J.K. Sprenger, A.S. Cavanagh, H. Sun, and S.M. George, J. Vac. Sci. Technol. A. 36, 01A118 (2018).