EFAB: A novel, high-aspect-ratio true three-dimensional microfabrication process for rapid, low-cost desktop micromachining of MEMS

Instant Masking, the core technique in EFAB (E&barbelow;lectrochemical FABrication), uses an Instant Mask to realize instant selective plating which speeds up present time-consuming 3-D fabrication processes. One method for fabrication of the silicone-base Instant Mask in presented in detail. Several basic performance characteristics of this Instant Mask were investigated. The major limitation of the Instant Mask is its short service lifetime due to delamination of the silicone rubber during Instant Masking plating. A BTA (Benzotriazole) surface modification method was proposed to extend the immersion lifetime of the Instant Mask in the plating bath.; The electrochemical polarization method was used to study the cathodic and anodic processes in Instant Masking plating. Proper bath selection and modification are critical in Instant Masking plating. The performance of bulk nickel plating was investigated by DC electrochemical methods to adjust the related process parameters for meeting EFAB requirements.; Internal stress in the deposits could cause failure of microstructures. The flexible strip method was employed to measure internal stresses in deposits produced under different conditions. The use of proper plating parameters and stress reducers can effectively reduce stress in the deposits. To obtain a layered microstructure, the adhesion between adjacent layers is very important. It was found that surface activation prior to plating is a critical step to achieve good adhesion. The effectiveness of several activation methods in increasing the adhesion of nickel deposits was evaluated by adhesion tests.; Diamond lapping was chosen as the planarization process. Its operation procedure and limitations are described. Copper etching is the last step in the EFAB process. Both chemical and electrochemical etching were studied and it was found that a commercial chemical etching product worked well for copper etching. The electrochemical etching tests indicated that electrochemical etching produced a higher etching rate than chemical etching. In addition, electrochemical etching can overcome a drawback of chemical etching, i.e., diffusion-limited etching.; In order to demonstrate the present capability of EFAB, SEM images showing several 3D microstructure produced using EFAB are presented.