Product category:
Simulation, modelling and validation software
News Release from: Vector Fields | Subject: Opera-3D
Edited by the Engineeringtalk Editorial
Team on 29 September 2004
Simulation helps reduce implanter design
cycles
Opera-3D is being used by Varian Semiconductor Equipment Associates to shorten the design cycle for new generations of ion implanters.
Opera-3D is being used by Varian Semiconductor Equipment Associates to shorten the design cycle for new generations of ion implanters Varian is an industry leader in design and manufacture of ion implant systems - semiconductor processing equipment used in the fabrication of integrated circuits
An important requirement is shorter beam lines to reduce effects of space charge and Tosca combined with Scala, both Vector Fields software packages, is used to predict the interaction of multiple magnets while simultaneously modelling the space charge of the ions, the trajectory of the ion beams and the electric fields within the implanter.
All of Varian's implanters work on the concept of pulling ions from a hot plasma source by means of extraction electrodes.
The ions pass through an acceleration/deceleration device that changes the energy of the beam, then through a number of magnetic fields for refinement and measurement.
The analyser magnet purifies the beam by filtering out contaminants; for example, if the source material is boron fluoride it will filter out the fluorine leaving only boron ions, the desired dopant.
Another magnet, called the corrector magnet, shapes the ion beam into the correct form for deposition onto the wafer.
The system includes other smaller magnets that perform functions such as measuring the ion dose.
Understanding the behaviour of both electric and magnetic fields is critical in the implanter design.
The system includes two sources of electric fields.
One is that created intentionally by the extraction electrodes, and another which occurs because the ions have a charge, so tend to repel each other.
This space charge effect must be counted so that the beam remains in focus as it passes through the implanter.
Saturation levels of the magnetic materials, which ensure the correct energy range of the beam and avoid aberrations and distortion, are also a vital design parameter.
The ultimate goal is to shape the beam so that it consistently delivers uniform, repeatable and correct dosage of dopant throughout the machine's life.
Following an initial sketch, a Tosca analysis enabled researchers to view the magnetic and electric fields and optimise each individual magnet - the source, the analyser, and the corrector as well as the other smaller elements.
Simulating then the magnets in close formation allowed a study of the interactions and a redesign of each segment to optimise the overall design yet achieve a prime goal of minimising beam length.
Scala, Vector Fields software which predicts space charge and ion trajectories simultaneously with magnetic and electric fields, helped Varian to achieve another design objective of neutralising space charge effects created by slower moving ions.
A lower energy beam was a desired parameter because it would make it possible to deposit the dopant in smaller depths, thus supporting customer demands for more densely packed chips.
A low energy beam however made space charge a more serious concern, because as ions travel more slowly they generate a greater space charge.
Having a shorter beam line would help, but designers still needed to neutralise the charge.
The combined effect of using the simulation tools from Vector Fields was a reduction in design time from months to days, the ability to investigate different magnetic configurations, which allowed the engineering team to quickly eliminate flawed ideas and concentrate only on innovative but effective solutions, and reduced time and costs of prototype builds, necessary with "trial and error" development methods.
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