Matthew Laudon

Mechanical characterization of a new high-aspect-ratio near UV-photoresist

Characterization of the mechanical and thermal properties of the high-aspect-ratio, negative, UV resist, SU-8 has been carried out. This resist allows for a broad range of thicknesses to be obtained with a single spin process. Standard exposure with a UV aligner has produced outstanding aspect ratios, 15 for lines and trenches. This type of performance lends itself well to MEMS applications, packaging, micromolds, spacers, etc. Because of the simplicity of use of the resist in addition to the large range of possible applications, the process dependent mechanical and thermal properties must be understood in order to completely exploit the potential of the resist.

VHDL–1076.1 modeling examples for microsystem simulation

Miniaturized, integrated sensors and actuators are a rapidly growing field with great future potential. To further promote their use, specialists must make them more accessible to system designers. This can be done through behavioral modeling of sensors and actuators using analog hardware description languages. The resulting models can be used in conjunction with models of the associated electronics to simulate a complete microsystem. This chapter presents VHDL 1076.1 modeling and simulation considerations applied to this field.

Modeling and Simulation of Electromechanical Transducers in Microsystems Using an Analogue Hardware Description Language

The analytical modeling and simulation of conservative electrostatic, electromagnetic and electrodynamic transducers found in microsystems using a non-linear lumped-parameter approach is presented in this paper. A comparison is made between this approach and the linearized equivalent circuit method. All models of transducers are written in HDL-A/sup TM/, a proprietary analogue hardware description language (HDL). System-level simulation is performed in the SPICE simulator using behavioral models of the transducers. Finally, a parameter extraction and HDL model generation tool for devices is presented.

Mechanical Response of X-Ray Masks

Overlay accuracy remains one of the major challenges in 1× lithography. In the case of X-ray masks, it is necessary to have a precise pattern on the mask itself and ensure that the pattern is not distorted due to mounting. A detailed study has been performed of the distortions induced in the membrane when the mask is held kinematically in various configurations, e.g., horizontal, vertical and inverted orientations (for e-beam writing, X-ray exposure and point source exposure, respectively). The new proposed X-ray mask standard has been used for all results presented. Finite element models were used to simulate alignment techniques and magnification correction procedures and subsequently determine maximum resultant distortions. Results show it necessary to optimize the mounting strategy to meet the stringent error budget required for 0.25 µm technology (and below).

Thermal characteristics of an R-ray mask during pattern transfer

Temperature gradients during mask fabrication can significantly affect the pattern fidelity of an X-ray mask. In order to minimize distortion effects, pattern transfer of the absorber must be done on a mask membrane. Temperature gradients also which occur during etch have an effect on both absorber feature size and profile. In addition, these gradients can result in variations in etch rate, which negatively impacts pattern placement. The purpose of this paper is to describe the thermal characteristics of a DARPA-NIST X-ray mask substrate during pattern transfer. The means for minimizing the observed gradient is also described.

Membrane distortions in x-ray masks due to specific absorber features

Finite element models have been created to investigate the local effect of pattern placement and absorber stresses. Models of an x-x ray mask membrane have been developed which include a centrally-located absorber strip. Using these models, the magnitude and location of the maximum in-plane distortions (IPD) and out-of-plane distortions (OPD) have been determined. The IPD data from the finite element models for the absorber strip have been compared to a closed-form analytical solution. In addition, the finite element models have been further developed to include feature patterns more closely resembling the absorber patterning used in the manufacturing of actual circuit designs. In this paper, finite element results of both the local and global in-plane distortions due to the placement of the numerous absorber features are presented. With these models it is possible to predict the distortion of the membrane due to absorber features prior to the construction of the mask, allowing this modeling process to be used as a predictive tool to correct for pattern placement errors in the e-beam writing process.

Capacitive detection method evaluation for silicon accelerometer by physical parameter extraction from finite element simulations

A capacitance evaluation method based on the extraction of physical parameters from finite element (FE) analysis is presented. Mechanical simulations and this capacitance evaluation method were applied to a new, highly symmetrical, silicon accelerometer in view of globally modeling the sensor system. The commercial hardware description language HDLA/sup TM/ is used to develop a compact behavioral macromodels for SPICE simulators.