Principal investigator: Dr Wang Xiaodong
Co-investigator: A/P Gong Haiqing, As/Prof Miao Jianmin
Date started: 11/1998
To develop a low temperature process for fabricating metallic MEMS.
There is a demand for metallic microstructures with relatively large thickness (i.e. 10-1000um) in the field of MEMS. For example, metallic microstructures with higher thickness are greatly needed in the actuation system where higher structural rigidity and/or higher actuation force is required. Metallic micro-nozzles and micro-channels, as the essential fluidic parts in inkjet heads, are tremendously required with the growth of printer market. Metallic microstructures with small feature and high aspect ratio are demanded as precise hot-embossing masters for plastic micromachining. The key process technology now has been successfully established in Micro Machines Laboratory (MML), School of MAE, NTU.
- Ultra-thick photoresist (Positive type: AZ9260 or Negative type: SU-8) is spun on metal-coated (seed layer) substrate.
- Normal photomask and UV mask aligner are employed to pattern the photoresist and form photoresist micro molds.
- Metal/alloy is electroformed into the photoresist micro molds.
- Photoresist molds are chemically stripped off and yield the final metallic microstructures.
Fig. 1: Basic steps of microelectroforming
- Magnetic sensors and actuators by electroforming magnetic materials.
- Hot embossing masters for micromahining plastics.
- Micromachined switch with high current transmission, micromirror and micromotor, etc.
- New generation inkjet printhead, integrally fabricated with nozzle plate and ink channel on single chip
- Flip-chip bonding
Fig. 2: 150um thick SU-8 photoresist molds
Fig. 3: A micromachined Ni micromotor
- Batch fabrication process
- Processes only need standard cleanroom facilities such as photomask, UV mask aligner, and electroplating system.
- Simple and low cost
- IC compatible, main processes are done at low temperature
- A variety of metals can be electroformed ( Ni, Cu, NiFe, Sn, Zn, etc).
- Movable structures can be realized by electroforming sacrificial and structural layers into same photoresist molds successively.