Advanced CAD System for Electromagnetic MEMS
Interactive Analysis (ACADEMIA)

Date: October 7, 1997

Introduction:

I. Accomplishments and Progress:

Task 1

There are a set of five subtasks listed in Attachment 1 that range from the building of tools and supporting infrastructure (i.e. geometry and grid servers) to model validation and application of the tools. During this first year primary emphasis was on the tool and infrastructure building aspects (as is also reflected in the start dates on the milestones). In addition, a compact modeling methodology was pursued as a means to hierarchically quantify the critical paths for development of FEM-based simulations.

1. demonstration of a compact model for the MEMS-based RF switch [1] that clearly parameterized the physical (and geometric) dependences
2. demonstration of a 2-3D geometry server, based on the level-set algorithm, that can capture physical details such as stress dependence during the deposition processes involved in fabricating MEMS devices [2]
3. prototype implementation of a 2D integrated geometry and grid server (the CAMINO tool) that can maintain persistence of data and accurately represent physical changes during typical MEMS process flows.
4. two prototyping activities in FEM-based analysis of the multi-physics for MEMS devices have been initiated: a) using ABAQUS the physical model formulation for stress dependent deposition is being investigated and b) using ProPHLEX a coupled electrostatic-elastostatic model for the MEMS RF switch is being prototyped.

Task 2

The essential objectives of this task relate to the extraction of materials properties of MEMS test structures that will directly support the FEM-based modeling from the constitutive equation formulation point of view, including reliability issues such as fracture and fatigue. Within the context of the test structures efforts discussed in Task 3, this task has added specific devices (and variations on existing geometries and processes) that will quantify the materials aspects.

1. a new analysis technique was developed for extraction of the unstrained lattice parameters of crystalline thin films and it has been applied in the extraction of residual stress of MEMS thin films.
2. a two mask-step process flow for analysis of fatigue in MEMS devices has been developed and the necessary test devices (and masks) are now being fabricated.

Task 3

The key objectives in this task are the implementation and evaluation of test structures that: monitor in-situ parameters and validate the modeling efforts both in terms of basic test devices and ones that more directly support the applications side. The geometry and process flow design is targeted to address issues of the RF switch as well as underlying quantification of limits for MEMS fabrication.

1. detailed study and evaluation of existing methods (test structures) used for parameter extraction, resulting in documentation of which structures are most suitable
2. design and implementation of a mask set containing an array of test devices that allow extraction of Young's Modulus and film stress information, both nominal and in comparison between different structures.

References:

[2] E. C. Kan, Z. K. Hsiau, V. Rao, and R. W. Dutton, "Gridding Techniques for the Level Set Method in Semiconductor Process and Device Simulation," 1997 Int'l Conf. on Simulation of Semiconductor Processes and Devices (SISPAD'97) Tech. Dig., p. 327, Sept. 1997.

II. Supporting Information

A. Technical Journals:

[2] G. Cornella, S-H Lee, W.D. Nix, and J.C. Bravman, "An analysis technique for extraction of thin film stresses from x-ray data," Appl. Phys. Lett., 71 (20), 1997.

B. Professional Personnel:

C. Interactions (and related activities):

[1] E. K. Chan, E. C. Kan, P. M. Pinsky and R. W. Dutton, "Nonlinear Dynamic Modeling of Micromachined Microwave Switches," MTT Conference, June 1997.

[2] E. C. Kan, Z. K. Hsiau, V. Rao, and R. W. Dutton "Gridding Techniques for the Level Set Method in Semiconductor Process and Device Simulation," 1997 Int'l Conf. on Simulation of Semiconductor Processes and Devices (SISPAD'97) Tech. Dig., p. 327, Sept. 1997.

2. Interactions:

a. Raytheon /TI (Greg Kovacs and group):

We are actively pursuing an effort with Raytheon/TI to explore a variety of metallic thin-films for structural and flexural members in RF switches. We have been assembling a semi-custom e-beam evaporator with ion gun to control stress. Unfortunately, our work has been delayed by persistent machine problems, which the manufacturer is now addressing. We expect to have the system on-line this month and be well away into the characterization.

b. MicroCosm interactions (Robert Dutton and group):

[1] Transferred 3D Oct-tree based level set boundary movement code to Microcosm. This code can perform 3D etching and deposition simulation on the level set grid. Its applications include KOH wet etching and APCVD silicon dioxide deposition simulations in 3D.

First order physical model for APCVD silicon dioxide deposition rates (curvature dependent) has been included. Physical models for wet etching rates and PVD tungsten/aluminum deposition rates will be developed.

[2] Discussed temperature dependency of LPCVD oxide models in SPEEDIE with Professor Chang Liu at University of Illinois. Professor Liu's group is using SPEEDIE for characterizing the temperature dependency in their oxide deposition process.

c. CFD Research Corporation interactions (Robert Dutton and group):

During the course of the first half of 1997 (January-June) the Stanford group, led by Dr. Edwin Kan, had extensive interactions with Dr. Andrzej Przekwas and Dr. Anantha Krishnan on issues of common procedural interfaces and supporting tools for Composite CAD interoperability. Both on the CFD Research and Stanford sides we have posted results of that dialog in terms of requirements associated with what has been called the "Tiger Team" efforts. This was also discussed at the last PI meeting at Stanford.

D. Discoveries/Inventions

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