Deposition Simulator DEP3D

Figure 1: Simulation of superconformal copper deposition into a trench pattern.
Figure 2: Example for simulated profiles (cross sections) of PECVD oxide layers deposited into rotationally symmetric contact holes at different positions on a wafer. The dark red region corresponds to the deposited oxide layer. The left side and the right side show the profiles at the wafer center and at the wafer rim, respectively.
Figure 3: Example for simulating the influence of the reactor pressure on the uniformity of a sputter-deposited metal layer.

The simulator DEP3D developed at Fraunhofer IISB allows one to simulate the shape of layers deposited on 3D features as encountered in semiconductor technology. The input as well as the output geometry are given as multi-layer structures which are modified by the deposited layer added on top.

DEP3D provides models for low-pressure chemical vapor deposition (LPCVD) [1], sputter deposition [2], superconformal CVD (Figure 1) [3], and plasma-enhanced CVD (PECVD) [4]. Furthermore, fast geometric operations such as conformal deposition (constant layer thickness everywhere on the structure) are supported. As an example, in Figure 2 the simulation of PECVD is shown [4]. The influence of the position of the contact hole on the wafer has been studied by coupling DEP3D with the plasma equipment simulator Q-VT from Quantemol.

In addition to modeling of profile evolution on feature scale, for physical vapor deposition, the accross-substrate uniformity of the layer thickness and its dependence on the reactor geometry and operating pressure can be simulated (Figure 3).

[1] E. Bär, J. Lorenz, 3D Simulation of Tungsten Low-Pressure Chemical Vapor Deposition in Contact Holes, Appl. Surf. Sci. 91 (1995) 321
[2] E. Bär, J. Lorenz, H. Ryssel, Three-Dimensional Simulation of Conventional and Collimated Sputter Deposition of Ti Layers into High Aspect Ratio Contact Holes, in: Proceedings of Conference on Simulation of Semiconductor Processes and Devices 1997 (SISPAD 1997), Technical Digest, IEEE, Piscataway, 1997, p. 297
[3] E. Bär, J. Lorenz, H. Ryssel, Three-Dimensional Simulation of Superconformal Copper Deposition Based on the Curvature-Enhanced Accelerator Coverage Mechanism, in: Copper Interconnects, New Contact Metallurgies/Structures, and Low-k Interlevel Dielectrics, Ed. G.S. Mathad, V. Bakshi, H.S. Rathore, K. Kondo, C. Reidsema-Simpson, Proc. Vol. 2003-10, The Electrochemical Society, Pennington, 2003, p. 21
[4] E. Baer, P. Evanschitzky, J. Lorenz, F. Roger, R. Minixhofer, L. Filipovic, R.L. de Orio, S. Selberherr, Coupled Simulation to Determine the Impact of across Wafer Variations in Oxide PECVD on Electrical and Reliability Parameters of Through-silicon Vias, Microelectronic Engineering 137 (2015) 141


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Example: Low-pressure Chemical Vapor Deposition (LPCVD) of Tungsten into a Contact Hole

Tungsten LPCVD Simulation

Blue: initial surface before deposition
Green: evolving surface of the deposited tungsten

DEP3D is applied to tungsten LPCVD using the reduction of tungsten hexafluoride (WF6) by silane (SiH4). We have found that an approach simulating the redistribution of the SiH4 molecules and assuming a constant reaction probability upon collision of a SiH4 molecule with the surface allows this process to be simulated with a reaction probability which is consistent with thermodynamic calculations.

In the simulation result, it can be seen that although the conformality is rather good, an enclosed gas volume (so-called void) remains after the opening of the hole is closed by the growing layer.

E. Bär, J. Lorenz, 3D Simulation of Tungsten Low-pressure Chemical Vapor Deposition in Contact Holes, Appl. Surf. Sci. 91 (1995) 321