How MEMS Sensors work
Technologies
Deep Reactive Ion Etching
Bosch engineering is continuously optimizing the use of DRIE to avail the potential of this enabling process. Numerous combinations of mask layers, etch stop, cleaning and characterization methods have been established. The MEMS community calls the resulting procedure the "Bosch Process".
Sacrificial etching
Isotropic etching of oxides or silicon is applied to realize movable MEMS structures or cavities
KOH etching
This anisotropic process is available for high volume throughput. Established procedures utilize KOH wet etching as well as electrochemical KOH etching with etch stop on depleted pn-transitions.
Wafer bonding
Wafer bonding techniques can be offered with different requirements and specifications e.g. bonding material (glas frit, anodic bonding), enclosed pressure and medium, alignment accuracy.
Metallization
Depending on the workflow IC compatible metals or „exotic“ materials like Pt can be used in established procedures including sputtering and etching techniques.
Lithography
Depending on the workflow a variety of lithography tools can be implemented.
- Mask alignment: 5x1 stepper, 1x1 projection, Proximity, backside alignment, IR alignment
- Coaters/Developers: standard spin coating, spray coating, wafer edge coating
Thin film deposition
A huge portfolio of deposition methods is available.
- Dielectrica: CVD-oxides and -nitrides, thermal oxides, etc.
- Silicon: LPCVD-poly, epitaxial silicon, Epi-poly with numerous options for doping
Experience
MEMS experience at Bosch goes back numerous generations of automotive sensors produced since 1994. Starting with integrated pressure sensors the product portfolio diversified rapidly. Today a large number of applications are based on Bosch‘s MEMS process platforms. Our process engineering is attended to the development and continuous optimisation of key MEMS technologies. A huge pool of experience is available in our R&D divisions.
Inertial sensors
Bosch‘s inertial sensors are based on surface micromachining. Key procedures like sacrificial etching or deep reactive ion etching have been developed to meet the demands of high volume throughput.
Pressure sensors
Pressure sensors have been realized in bulk and surface micromaching techniques making use of optimized thin film properties and reliable batch processes concepts.