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Designed to enable the fabrication of all Si etch devices, Deep Silicon Etching delivers:
Deep Reactive Ion etching of Silicon (DRIE), or Deep Silicon Etching (DSiE), is a highly anisotropic etch process used to create deep, steep-sided holes and trenches in wafers/substrates, typically with high aspect ratios.
The Estrelas® DSiE system offers ultimate process flexibility, serving multiple process solutions across the Micro Electro Mechanical Systems (MEMS), Advanced Packaging and Nanotechnology markets.
The two technologies used to achieve deep etches in the fabrication of micro-electro-mechanical systems (MEMS) are the Bosch and the Cryogenic Processes. System and process development over many years has allowed the techniques to advance but the fundamental aspects of each remain the same:
The Bosch process uses a fluorine based plasma chemistry to etch the silicon, combined with a fluorocarbon plasma process to provide sidewall passivation and improved selectivity to etch mask. A complete etch process cycles between etch and deposition steps many times to achieve deep, vertical etch profiles. It relies on the source gases being broken down in a high-density plasma region before reaching the wafer.
This technique cannot be performed in reactive ion etch systems (RIE), as these have the wrong balance of ions to free radical species. This balance can be achieved in high-density plasma systems (HDP). The most widely used form of HDP uses inductive coupling to generate the high-density plasma region so is known as ‘inductively coupled plasma’ (ICP).
High rate, controlled scallops e.g. Microfluidics (200 µm depth), vias (> 400 µm depth)
Microneedles created using the Bosch process
Just as for the Bosch process, this technique also uses SF6 to provide fluorine radicals for silicon etching. The silicon is removed in the form of SiF4, which is volatile.
The main difference is in the mechanism of sidewall passivation and mask protection. Rather than using a fluorocarbon polymer, this process relies on forming a blocking layer of oxide/fluoride (SiOxFy) on the sidewalls (around 10-20nm thick), this forms at the cryogenic temperatures used and the layer inhibits the attack on the underlying Si layer by the fluorine radicals.
The low temperature and low bias operation also assists in reducing the etch rate of the mask material, which is normally either photoresist or silicon dioxide.
Micro-mould created using the Cryo process
Si waveguide etch
Smooth sidewall cryogenic DSE (no scallops).
Courtesy TU Twente
The PlasmaPro 100 Estrelas platform is designed to give total flexibility for Deep Reactive Ion Etching (DRIE) applications - serving a diverse set of process requirements across the Micro Electromechanical Systems (MEMS), Advanced Packaging and Nanotechnology markets. Developed for research and volume production, the PlasmaPro 100 Estrelas offers the ultimate flexibility with Bosch and Cryogenic processes.
DSiE technique or Deep Reactive Ion Etching (DRIE) combines isotropic silicon etching and passivation steps repeatedly to obtain anisotropic profiles. Using high density plasma source and fast gas-switching capability, this technique enables you to achieve profile verticality, smooth sidewalls and high etching rates with high selectivity to masking materials.
From smooth sidewall processes to high rate cavity etches and high aspect ratio processes to tapered via etches, the PlasmaPro 100 Estrelas has been designed to ensure that the wide range of applications in MEMS, advanced packaging and nanotechnology can be realised without the need to change chamber hardware.
Nano and microstructures can be realised as the hardware has been designed with the ability to run Bosch™ and Cryo etch technologies in the same chamber.
Cryogenic DSiE is typically used for smooth sidewalls and/or nano-etching and temperature sensitive materials, as it provides low temperature process (» -110°C)
|
|
Cryogenic |
| |||
Rate (μm/min) |
High |
Moderate |
Low | |||
Selectivity to PR |
Very high |
High |
Low | |||
Profile |
|
Vertical or Sloped |
Vertical or Sloped | |||
Aspect ratio |
Very high |
High |
Low | |||
Sidewalls |
Scallops |
Smooth |
Smooth | |||
ARDE control |
Yes |
Limited |
Limited | |||
Cleaning |
Regular |
Rare |
Regular | |||
Min. feature /nm |
≈ 300 |
≈ 10 |
30 |
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Gas pod - incorporate extra gas lines and allow greater flexibility
Logviewer software - datalogging software allows realtime graphing and post run analysis
Optical end point detectors - an important tool for achieving optimal process results
Soft pump - allows the slow pumping down of a vacuum chamber
Turbomolecular vacuum pump - offers superior pumping speeds and higher throughput
X20 Control System - delivers a future proof, flexible and reliable tool with increased system ‘intellect’
Advanced Energy Paramount generator - Offering increased reliability and greater plasma stability
Automatic pressure control - This controller ensures very fast and accurate pressure control
Dual CM gauge switching - provides the ability to utilise two differing ranges of capacitance manometer via a single pressure control valve
LN2 autochangeover unit - enables table cooling fluid to be automatically switched between Liquid Nitrogen (LN2) and Chiller Fluid
Wide temperature range electrode - significant design improvements to increase process performance
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