This paper aims to fabricate high aspect ratio through silicon via (TSV) by photo-assisted electrochemical etching (PAECE) and supercritical CO2 copper electroplating. A blind-holed silicon array was first fabricated by PAECE. By studying the etching parameters, including hydrofluoric acid concentration, etchant temperature, stirring speed, tetrabutylammonium perchlorate (TBAP) content, and Ohmic contact thickness, an array of pores with a 1∶45 aspect ratio (height=250 μm and diameter=5.5 μm) was obtained successfully. Moreover, TBAP and Kodak Photo-Flo (PF) solution were added into the etchant to acquire smooth sidewalls for the first time. TBAP was added for the first time to serve as an antistatic agent in deionized water-based etchant to prevent side-branch etching, and PF was used to degasify hydrogen bubbles in the etchant. The effect of gold thickness over Ohmic contact was investigated. Randomized etching was observed with an Au thickness of 200 Å, but it can be improved by increasing the etching voltage. The silicon mold of through-holes was filled with metal using supercritical CO2 copper electroplating, which features high diffusivity, permeability, and density. The TSV structure (aspect ratio=1∶35) was obtained at a supercritical pressure of 2000 psi, temperature of 50°C, and current density of 30 mA/cm2 in 2.5 h.
This paper reports a novel external cavity diode laser system for applications in atomic physics that employs a
micromachined silicon flexure to sweep the laser frequency near the rubidium absorption spectrum. The advantages of
using a silicon flexure are its simple microfabrication process and reduction of the overall size of the laser system. The
results demonstrate the 87Rb, 85Rb (rubidium) D2 line absorption at 780 nm in an atomic optics test experiment. Our
novel laser system design has a size of 26.3 x 20 x 20 mm. The wavelength can be tuned and swept from 780.2533 to
780.2344 nm equivalent to 9.31 GHz using only piezoelectric transducer PZT actuators integrated on the silicon flexure.
The deflection of the silicon flexure is 157.45 nm. The advantage of combining a VHG and a silicon flexure is that the
frequency can be coarsely tuned to 780.24 nm and swept at this center frequency with a range of 9.31 GHz by PZT.
Moreover, the frequency fine tuning can be achieved by changing the VHG temperature to observe the rubidium
spectrum. The laser output power is measured as 9.72 mW at 780.24385 nm.