Ultrafine Silicon Nano-wall Hollow Needles and Applications in Inclination Sensor and Gas Transport
- PDF / 323,590 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 64 Downloads / 163 Views
Ultrafine Silicon Nano-wall Hollow Needles and Applications in Inclination Sensor and Gas Transport Z. Sanaee, S. Mohajerzadeh, M. Mehran and M. Araghchini Nanoelectronic Center of Excellence, Thin Film and Nano-Electronic Laboratory, School of Electrical & Computer Engineering, University of Tehran, Tehran, Iran ABSTRACT We report on the realization of high precision hollow structures directly on silicon suitable for liquid and gas/vapor transport. The formation of hollow structures requires high aspect ratio etching combined with bulk back-side micro-machining to realize silicon-based membranes. The use of a slant angle deposition method has been used as an alternative method for three-dimensional lithography. The transfer of acetone vapor through such tiny holes shows an anomalous behavior where a sharp rise is observed followed by an exponential and gradual decay. These structures can be eventually used as mass ion separation devices. INTRODUCTION Smart drug delivery depends on the evolution of hollow micro-needles [1]. The transfer of drug through little holes inside such structures allows a replacement for regular injection needles [2, 3]. In addition, the contact between the electrodes and the patient’s body in electrocardiograph units is usually made through a gel surface. Micro-needles are considered as possible alternatives to replace the electrolytic gel, where they can penetrate through the outer layer of skin and improve the electrical contacts with no need to an externally applied gel [4]. Apart from biological applications, the cup-like structures can be used as gas and vapor transfer media for mass spectroscopy and ionization sources [5]. We report a method to realize ultrafine hollow needle structures on silicon-based membranes. Such structures were used for liquid and gas transport showing anomalous behavior. EXPERIMENT High aspect ratio deep etching of silicon is used to fabricate hollow micro-needle. Deep etching of Si has been practiced using a modified reactive ion etching method where a combination of H2/O2/SF6 gases is used to perform passivation and SF6 gas for etching step in fully programmable sub-cycles and in a sequential manner. These passivation/ etching sub-cycles should be repeated as many times to achieve desired depth. Details about this technique can be found elsewhere [6]. The fabrication starts by cleaning (100)-Si wafers followed by E-beam deposition of Cr as the mask for future processing. Circular hollow rings with outer diameter of 3-40 μm and rim widths less than 200 nm are created using projection lithography. Once vertical pipe-like structures are
123
created, a slant-angle rotation and deposition method is used to cover the surface of the samples with Cr except for the inner surfaces. As a result only the outer sides of the recessed craters are coated while inner parts and especially the inner bottom remains uncoated. Since the bottom of each micro cylinder is not coated with Cr, the etching can be continued on these surfaces without affecting the other parts of the s
Data Loading...
