(Color online) Axially stacked wafers contain holes, hence form one tube with each of the holes (Ref. 1 ).
(Color online) Technique of photolithography.
(Color online) Mask used during photolithography.
(Color online) Schematic diagram of DRIE with inductive coil which is not present in RIE.
Hole characteristics measured using SEM.
Slanting edges of etched oxide.
Reactive ion etching result after 1 h of RIE with process pressure of 150 mT, RF power at 150 W, CF4 flow of 30 sccm, and O2 flow of 2 sccm. Oxide angle after RIE was closer to 90° as compared with earlier attempts of wet etching.
Irregular wet etching of Cr mask.
Example of an unsuccessful Cr lift off.
(Color online) Examples of ripping effect: (a) Cr thin film sputtered on SU8 that is patterned on Si, (b) ripped Cr on Si after lift-off, (c) top view of wafer after lift off.
Example of scalloping in Bosch technique. (Dust particles appearing in the image should be neglected.)
Base etch results in which temperature was −95 °C, pressure was 12 mT, total gas flow (SF6 + O2) was 76 sccm, O2 percentage in gas was 7.9%, RF power was 3 W, and ICP power was 700 W.
Result of calibration etches: (a) Higher pressure, (b) higher temperature than base recipe.
Result of final etch recipe in which temperature was −90 °C, pressure was 14 mT, total gas flow (SF6 + O2) was 76, O2 percentage in gas was 7.9%, RF power was 3 W, and ICP power was 700 W.
Example of notching and bowing occuring in an etched sample.
(a) Holes etched 306 μm in 120 min. (b) Trenches etched 358 μm in 120 min.
(Color online) Stack of three bonded dies.
Results with higher pressure and higher temperature than the base variables after calibration etches.
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